Data processing method and device to resolve packet loss in multi-hop link system

ABSTRACT

A data processing method, where a first device communicates with a second device using a relay node, where the relay node does not have a Packet Data Convergence Protocol (PDCP) entity, and the method includes transmitting, by the first device, a first data unit group, where the first data unit group is in a first sequence range, receiving, by the first device, first information using the relay node, where the first information indicates a data unit that the second device has received or has not received in the first data unit group, determining, by the first device, a second sequence range based on the first information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage of International PatentApplication No. PCT/CN2019/085868 filed on May 7, 2019, which claimspriority to Chinese Patent Application No. 201810444917.9 filed on May10, 2018. Both of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

This application relates to the communications field, and morespecifically, to a data processing method and a device.

BACKGROUND

To ensure deployment and application of a future cellular network, atechnology supporting a wireless backhaul and relay link is provided ina 5th generation (5 Generation, 5G) new radio (New Radio, NR)technology. As an integrated access and backhaul (Integrated Access andBackhaul, IAB) technology, this technology can provide denser and moreflexible deployment of NR cells, without a massive increase of transportnetworks. In an IAB network structure, a donor base station (Donor 5GNodeB, DgNB) may be directly connected to a core network, and may beconnected to a plurality of relay nodes (Relay Node, RN), and the relaynodes may be connected to other relay nodes. Links between base stations(including a link between the donor base station and a relay node and alink between relay nodes) are referred to as backhaul (Backhaul) links.Links between user equipment and base stations (including a link betweenthe donor base station and the user equipment and a link between a relaynode and the user equipment) are referred to as access (Access) links.The user equipment (User Equipment, UE) may be connected to the donorbase station or a relay node. A direct connection between the userequipment and the donor base station is a one-hop link. The userequipment may be further connected to the donor base station by usingone or more relay nodes. In this case, the connection is a multi-hoplink.

In a long term evolution (Long Term Evolution, LTE) system, userequipment may be directly connected to a base station, or user equipmentmay be connected to a base station by using a relay node. In the longterm evolution (Long Term Evolution, LTE) system, the relay node is alayer 3 relay node in a protocol stack, and its radio link control(Radio Link Control, RLC) is responsible for reordering received datapackets that are disordered, and delivering the data packets to a packetdata convergence protocol (Packet Data Convergence Protocol, PDCP) layerabove the RLC layer. In NR in a 5G system, a relay node is a layer 2relay node in a protocol stack, and its RLC layer has no reorderingfunction. Therefore, when data processing is performed by user equipmentand a donor base station on a multi-hop link in the 5G system, a packetloss problem is caused. This severely affects accuracy of datatransmission, and reduces communication efficiency, resulting in pooruser experience.

SUMMARY

This application provides a data processing method and a device toresolve a packet loss problem generated when data processing isperformed by user equipment and a donor base station in a multi-hop linkin a 5G system, improve accuracy of data transmission and efficiency ofdata transmission, and improve user experience.

According to a first aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

the first device transmits a first data unit group, where the first dataunit group is in a first sequence range;

the first device receives first information by using the at least onerelay node, where the first information is used to indicate a data unitthat the second device has received and/or has not received in the firstdata unit group; and

the first device determines a second sequence range based on the firstinformation.

In the technical solution of this embodiment of this application, thefirst device may transmit data units in the first sequence range, andthe first device determines the second sequence range based on the firstinformation about the data unit that the second device has receivedand/or has not received in the first data unit group, thereby avoiding apacket loss problem generated because a data unit is beyond a receivewindow of a receive end, and improving accuracy of data transmission andefficiency of data transmission.

It should be understood that in an uplink transmission scenario, thefirst device may be a terminal device, and the second device may be abase station. The terminal device transmits a first data unit group,where the first data unit group is in a first sequence range; theterminal device receives first information by using the at least onerelay node, where the first information is used to indicate a data unitthat the donor base station has received and/or has not received in thefirst data unit group; and the terminal device determines a secondsequence range based on the first information.

In a downlink transmission scenario, the first device may be a donorbase station, and the second device may be a terminal device. The donorbase station transmits a first data unit group, where the first dataunit group is in a first sequence range; the donor base station receivesfirst information by using the at least one relay node, where the firstinformation is used to indicate a data unit that the terminal device hasreceived and/or has not received in the first data unit group; and thedonor base station determines a second sequence range based on the firstinformation.

With reference to the first aspect, in a first possible implementationof the first aspect, that the first device determines a second sequencerange based on the first information includes:

if the first information includes information about successful receptionof N consecutive data units starting from the first data unit in thefirst sequence range, the first device obtains the second sequence rangeby shifting the first sequence range by N sequences, where N is apositive integer.

With reference to the first aspect or the first possible implementationof the first aspect, in a second possible implementation, that the firstdevice receives first information by using the at least one relay nodeincludes:

the first device receives a first message transmitted by the seconddevice and forwarded by the at least one relay node, where the firstmessage includes the first information.

With reference to the second possible implementation of the firstaspect, in a third possible implementation, the first message is astatus report of a PDCP entity; or

the first message is a status report of a radio link control RLC entity.

With reference to the first aspect or the first possible implementationof the first aspect, in a fourth possible implementation, that the firstdevice receives first information by using the at least one relay nodeincludes:

the first device receives a second message obtained by the at least onerelay node based on a first message transmitted by the second device,where the second message includes the first information.

With reference to the fourth possible implementation of the firstaspect, in a fifth possible implementation, the second message isdetermined by the at least one relay node based on the first message anda mapping relationship between numbers of data units transmitted andreceived that is maintained by the at least one relay node.

With reference to the fifth possible implementation of the first aspect,in a sixth possible implementation, the second message is a statusreport of an RLC entity.

With reference to the second or the third possible implementation of thefirst aspect, in a seventh possible implementation, the first message isa periodically transmitted message.

In the technical solution of this embodiment of this application, thefirst message is periodically transmitted to ensure stability of acommunications system.

With reference to the second possible implementation of the firstaspect, in an eighth possible implementation, before the first devicereceives the first message from the second device and forwarded by theat least one relay node, the method further includes:

the first device transmits a query request to the second device.

According to a second aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

a first relay node receives first information transmitted by aprevious-hop relay node of the first relay node or the second device,where the first information is used to indicate a data unit that thesecond device has received and/or has not received in a first data unitgroup, and the first data unit group is in a first sequence range; and

the first relay node forwards the first information.

In the technical solution of this embodiment of this application, thefirst device may transmit data units in the first sequence range, andthe first device determines a second sequence range based on the firstinformation about the data unit that the second device has receivedand/or has not received in the first data unit group, where the firstinformation transmitted by the second device is forwarded by the firstrelay node to the first device, thereby avoiding a packet loss problemgenerated because a data unit is beyond a receive window of a receiveend, and improving accuracy of data transmission and efficiency of datatransmission.

According to a third aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

a first relay node receives first information transmitted by the seconddevice, where the first information is used to indicate a data unit thatthe second device has received and/or has not received in a first dataunit group, and the first data unit group is in a first sequence range;and

the first relay node transmits second information, where the secondinformation is determined based on a mapping relationship betweennumbers of data units transmitted and received that is maintained by thefirst relay node and the first information.

In the technical solution of this embodiment of this application, thefirst device may transmit data units in the first sequence range, andthe first device determines a second sequence range based on the firstinformation about the data unit that the second device has receivedand/or has not received in the first data unit group, where the firstrelay node obtains the second information by processing the firstinformation transmitted by the second device, thereby avoiding a packetloss problem generated because a data unit is beyond a receive window ofa receive end, and improving accuracy of data transmission andefficiency of data transmission.

According to a fourth aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

a first relay node receives a first data unit group transmitted by thefirst device, and

the first relay node adds numbers to data units in the first data unitgroup.

In the technical solution of this embodiment of this application, thefirst relay node can add numbers to data units, thereby avoiding apacket loss problem generated because a data unit is beyond a receivewindow of a receive end, and improving accuracy of data transmission andefficiency of data transmission.

It should be understood that the first relay node may be a relay nodethat directly communicates with the first device.

With reference to the fourth aspect, in a first possible implementationof the fourth aspect, that the first relay node adds numbers to dataunits in the first data unit group includes:

the first relay node adds the numbers to the data units in the firstdata unit group based on receiving order.

With reference to the fourth aspect or the first possible implementationof the fourth aspect, in a second possible implementation, before thefirst relay node adds numbers to data units in the first data unitgroup, the method further includes:

the first relay node orders the data units in the first data unit group.

With reference to the fourth aspect, or the first or the second possibleimplementation of the fourth aspect, in a third possible implementation,an adaptation layer of the first relay node has an ordering function; or

a radio link control RLC entity of the first relay node has an orderingfunction; and/or

the adaptation layer of the first relay node has a numbering function.

For example, the adaptation layer of the first relay node has thenumbering function or the ordering function.

For example, the adaptation layer of the first relay node has thenumbering function and the ordering function.

For example, the radio link control RLC entity of the first relay nodehas the ordering function, and the adaptation layer of the first relaynode has the numbering function.

For example, the radio link control RLC entity of the first relay nodehas the ordering function, or the adaptation layer of the first relaynode has the numbering function.

With reference to the third possible implementation of the fourthaspect, in a fourth possible implementation, the adaptation layer islocated above the radio link control RLC entity.

With reference to the third possible implementation of the fourthaspect, in a fifth possible implementation, the adaptation layer islocated above a media access control MAC entity.

According to a fifth aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

a second relay node receives a data unit transmitted by a relay nodethat is connected to the second relay node, where the data unit has anumber; and

the second relay node orders the data unit having the number.

In the technical solution of this embodiment of this application, thesecond relay node can order data units that have numbers, therebyavoiding a packet loss problem generated because a data unit is beyond areceive window of a receive end, and improving accuracy of datatransmission and efficiency of data transmission.

It should be understood that the second relay node may be anintermediate relay node, that is, a relay node that does not directlycommunicate with the first device or the second device.

With reference to the fifth aspect, in a first possible implementationof the fifth aspect, the number is added by a first relay node, and thefirst relay node is a relay node that directly communicates with theterminal device; or

the number is added by a relay node that directly communicates with thesecond relay node.

With reference to the fifth aspect or the first possible implementationof the fifth aspect, in a second possible implementation, an adaptationlayer of the second relay node has an ordering function; or

a radio link control RLC entity of the second relay node has an orderingfunction.

With reference to the second possible implementation of the fifthaspect, in a third possible implementation, the adaptation layer islocated above the radio link control RLC entity.

With reference to the second possible implementation of the fifthaspect, in a fourth possible implementation, the adaptation layer islocated above a media access control MAC entity.

According to a sixth aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

a first relay node receives a data unit having a number and transmittedby the at least one relay node;

the first relay node orders the data unit based on the number; and

the first relay node transmits a first data unit group to the firstdevice in order based on the number, where the first data unit groupincludes the ordered data unit.

In the technical solution of this embodiment of this application, thefirst relay node can add numbers to data units or order data units,thereby avoiding a packet loss problem generated because a data unit isbeyond a receive window of a receive end, and improving accuracy of datatransmission and efficiency of data transmission.

With reference to the sixth aspect, in a first possible implementationof the sixth aspect, the number is added by an adaptation layer of thesecond device.

With reference to the sixth aspect, in a second possible implementationof the sixth aspect, an adaptation layer of the first relay node has anordering function; or

a radio link control RLC entity of the first relay node has an orderingfunction.

With reference to the second possible implementation of the sixthaspect, in a third possible implementation, the adaptation layer islocated above the radio link control RLC entity.

With reference to the second possible implementation of the sixthaspect, in a fourth possible implementation, the adaptation layer islocated above a media access control MAC entity.

According to a seventh aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

a second relay node receives a data unit transmitted by a relay nodethat is connected to the second relay node, where the data unit has anumber; and

the second relay node orders the data unit having the number.

In the technical solution of this embodiment of this application, thesecond relay node can order data units that have numbers, therebyavoiding a packet loss problem generated because a data unit is beyond areceive window of a receive end, and improving accuracy of datatransmission and efficiency of data transmission.

With reference to the seventh aspect, in a first possible implementationof the seventh aspect, the number is added by an adaptation layer of thesecond device; or

the number is added by a relay node that directly communicates with thesecond relay node.

With reference to the first possible implementation of the seventhaspect, in a second possible implementation, an adaptation layer of thesecond relay node has an ordering function; or

a radio link control RLC entity of the second relay node has an orderingfunction.

With reference to the second possible implementation of the seventhaspect, in a third possible implementation, the adaptation layer islocated above the radio link control RLC entity.

With reference to the second possible implementation of the seventhaspect, in a fourth possible implementation, the adaptation layer islocated above a media access control MAC entity.

According to an eighth aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

the first device receives a third message, where the third messageincludes hop count information for communication between the firstdevice and the second device; and

the first device determines a first sequence range based on the hopcount information, where the first sequence range is used to indicate arange of sequence numbers allocated by the first device.

In the technical solution of this embodiment of this application, amaximum quantity of data units that a transmit end is allowed totransmit is controlled, thereby avoiding a packet loss problem generatedbecause a data unit is beyond a receive window of a receive end, andimproving accuracy of data transmission and efficiency of datatransmission.

With reference to the eighth aspect, in a first possible implementationof the eighth aspect, the first sequence range is less than or equal toa quantity of allocated sequence numbers, and the quantity of allocatedsequence numbers is a sequence number space divided by a hop count andthen divided by 2.

With reference to the eighth aspect or the first possible implementationof the eighth aspect, in a second possible implementation, the thirdmessage is a broadcast message.

With reference to the eighth aspect or the first possible implementationof the eighth aspect, in a third possible implementation, the thirdmessage is a message transmitted by using dedicated signaling.

With reference to the eighth aspect, or the first, the second, or thethird possible implementation of the eighth aspect, in a fourth possibleimplementation, the third message is transmitted by the second device.

With reference to the eighth aspect, or the first, the second, or thethird possible implementation of the eighth aspect, in a fifth possibleimplementation, the third message is transmitted by the at least onerelay node.

According to a ninth aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

a first relay node determines first hop count information, where thefirst relay node is a relay node that directly communicates with thefirst device; and

the first relay node transmits a third message to the first device,where the third message includes the first hop count information, where

the first hop count information is a quantity of the at least one relaynode or a quantity of the at least one relay node plus 1.

In the technical solution of this embodiment of this application, aquantity of data units at a transmit end is controlled, thereby avoidinga packet loss problem generated because a data unit is beyond a receivewindow of a receive end, and improving accuracy of data transmission andefficiency of data transmission.

With reference to the ninth aspect, in a first possible implementationof the ninth aspect, the transmitting a third message to the firstdevice includes:

transmitting the third message to the first device by broadcast.

With reference to the ninth aspect, in a second possible implementationof the ninth aspect, the transmitting a third message to the firstdevice includes:

transmitting the third message to the first device by using dedicatedsignaling.

With reference to the ninth aspect, in a third possible implementationof the ninth aspect, that the first relay node determines the first hopcount information includes:

the first relay node obtains the first hop count information by adding 1to second hop count information broadcast by a previous-hop relay nodeof the first relay node.

According to a tenth aspect, a data processing method is provided. Inthe method, a first device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

the first device receives, by using the at least one relay node, a firstdata unit transmitted by the second device, where the first data unitcarries a count value; and

the first device processes the first data unit based on the count valuecarried in the first data unit.

In the technical solution of this embodiment of this application, amaximum edge of a transmit window exists at a transmit end, a maximumedge of a receive window does not exist at a receive end, and a dataunit carrying a count value is transmitted, so that the data unit isprocessed, thereby avoiding a packet loss problem generated because adata unit is beyond the receive window of the receive end, and improvingaccuracy of data transmission and efficiency of data transmission.

With reference to the tenth aspect, in a first possible implementationof the tenth aspect, that the first device processes the first data unitbased on the count value carried in the first data unit includes:

if the count value of the first data unit is greater than a count valuenext to a count value of a last data unit currently already delivered,storing the first data unit; or

if the count value of the first data unit is equal to a count value nextto a count value of a last data unit currently already delivered,delivering the first data unit to an upper layer of a packet dataconvergence protocol PDCP entity; or

if the count value of the first data unit is less than a count valuenext to a count value of a last data unit currently already delivered,discarding the first data unit.

With reference to the first possible implementation of the tenth aspect,in a second possible implementation, the method further includes:

storing the first data unit, and delivering the first data unit to theupper layer of the PDCP entity in order based on the count value of thefirst data unit.

With reference to the tenth aspect, or the first or the second possibleimplementation of the tenth aspect, in a third possible implementation,the first data unit is in the first sequence range.

With reference to the third possible implementation of the tenth aspect,in a fourth possible implementation, the first sequence range indicatesa range of count values that the second device is allowed to allocate ora range of count values that the second device is allowed to allocatewhen transmitting the first data unit.

With reference to the third or the fourth possible implementation of thetenth aspect, in a fifth possible implementation, a size of the firstsequence range is half of a sequence number space or less than half of asequence number space.

According to an eleventh aspect, a data processing method is provided.In the method, a first device communicates with a second device by usingat least one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The method includes:

the second device transmits a first data unit to the first device byusing the at least one relay node, where the first data unit carries acount value, where

the first data unit belongs to a first sequence range, and the firstsequence range is used to indicate a range of count values that thesecond device is allowed to allocate.

With reference to the eleventh aspect, in a first possibleimplementation of the eleventh aspect, a size of the first sequencerange is half of a sequence number space or less than half of a sequencenumber space.

According to a twelfth aspect, a communications device is provided. Thecommunications device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver module, configured to transmit a first data unit group,where the first data unit group is in a first sequence range, where

the transceiver module is further configured to receive firstinformation by using the at least one relay node, where the firstinformation is used to indicate a data unit that the second device hasreceived and/or has not received in the first data unit group; and

a processing module, configured to determine a second sequence rangebased on the first information.

With reference to the twelfth aspect, in a first possible implementationof the twelfth aspect, the processing module is further configured to:

if the first information includes information about successful receptionof N consecutive data units starting from the first data unit in thefirst sequence range, obtain the second sequence range by shifting thefirst sequence range by N sequences, where N is a positive integer.

With reference to the twelfth aspect or the first possibleimplementation of the twelfth aspect, in a second possibleimplementation, the transceiver module is further configured to:

receive a first message transmitted by the second device and forwardedby the at least one relay node, where the first message includes thefirst information.

With reference to the second possible implementation of the twelfthaspect, in a third possible implementation, the first message is astatus report of a PDCP entity; or

the first message is a status report of a radio link control RLC entity.

With reference to the twelfth aspect or the first possibleimplementation of the twelfth aspect, in a fourth possibleimplementation, the transceiver module is further configured to receivea second message obtained by the at least one relay node based on afirst message transmitted by the second device, where the second messageincludes the first information.

With reference to the fourth possible implementation of the twelfthaspect, in a fifth possible implementation, the second message isdetermined by the at least one relay node based on the first message anda mapping relationship between numbers of data units transmitted andreceived that is maintained by the at least one relay node.

With reference to the fifth possible implementation of the twelfthaspect, in a sixth possible implementation, the second message is astatus report of an RLC entity.

With reference to the second or the third possible implementation of thetwelfth aspect, in a seventh possible implementation, the first messageis a periodically transmitted message.

With reference to the second possible implementation of the twelfthaspect, in an eighth possible implementation, the communications devicefurther includes:

a querying module, configured to transmit a query request to the seconddevice.

According to a thirteenth aspect, a communications device is provided. Afirst device communicates with a second device by using at least onecommunications device, and the at least one communications device doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver module, configured to receive first informationtransmitted by a previous-hop relay node of the first relay node or thesecond device, where the first information is used to indicate a dataunit that the second device has received and/or has not received in afirst data unit group, and the first data unit group is in a firstsequence range, where

the transceiver module is further configured to forward the firstinformation.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

According to a fourteenth aspect, a communications device is provided. Afirst device communicates with a second device by using at least onecommunications device, and the at least one communications device doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver module, configured to receive first informationtransmitted by the second device, where the first information is used toindicate a data unit that the second device has received and/or has notreceived in a first data unit group, and the first data unit group is ina first sequence range; and

a processing module, configured to generate a second message, where thesecond information is determined based on a mapping relationship betweennumbers of data units transmitted and received that is maintained by thecommunications device and the first information, where

the transceiver module is further configured to transmit the secondinformation.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

According to a fifteenth aspect, a communications device is provided. Afirst device communicates with a second device by using at least onecommunications device, and the at least one communications device doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver module, configured to receive a first data unit grouptransmitted by the first device; and

a processing module, configured to add numbers to data units in thefirst data unit group.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

With reference to the fifteenth aspect, in a first possibleimplementation of the fifteenth aspect, the processing module is furtherconfigured to add the numbers to the data units in the first data unitgroup based on receiving order.

With reference to the fifteenth aspect or the first possibleimplementation of the fifteenth aspect, in a second possibleimplementation, the processing module is further configured to order thedata units in the first data unit group.

With reference to the fifteenth aspect, or the first or the secondpossible implementation of the fifteenth aspect, in a third possibleimplementation, an adaptation layer of the communications device has anordering function; or

a radio link control RLC entity of the communications device has anordering function; and/or

the adaptation layer of the communications device has a numberingfunction.

With reference to the third possible implementation of the fifteenthaspect, in a fourth possible implementation, the adaptation layer islocated above the radio link control RLC entity.

With reference to the third possible implementation of the fifteenthaspect, in a fifth possible implementation, the adaptation layer islocated above a media access control MAC entity.

According to a sixteenth aspect, a communications device is provided. Afirst device communicates with a second device by using at least onecommunications device, and the at least one communications device doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver module, configured to receive a data unit transmitted by arelay node that is connected to the communications device, where thedata unit has a number; and

a processing module, configured to order the data unit having thenumber.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the second relay node, that is, the communicationsdevice may be an intermediate relay node.

With reference to the sixteenth aspect, in a first possibleimplementation of the sixteenth aspect, the number is added by a firstrelay node, and the first relay node is a relay node that directlycommunicates with the first device; or

the number is added by a relay node that directly communicates with thecommunications device.

With reference to the first possible implementation of the sixteenthaspect, in a second possible implementation, an adaptation layer of thefirst relay node has an ordering function; or

a radio link control RLC entity of the first relay node has an orderingfunction; and/or

the adaptation layer of the first relay node has a numbering function.

With reference to the sixteenth aspect or the first possibleimplementation of the sixteenth aspect, in a third possibleimplementation, an adaptation layer of the communications device has anordering function; or

a radio link control RLC entity of the communications device has anordering function.

With reference to the second or the third possible implementation of thesixteenth aspect, in a fourth possible implementation, the adaptationlayer is located above the radio link control RLC entity.

With reference to the second or the third possible implementation of thesixteenth aspect, in a fifth possible implementation, the adaptationlayer is located above a media access control MAC entity.

According to a seventeenth aspect, a communications device is provided.A first device communicates with a second device by using at least onecommunications device, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver module, configured to receive a data unit having a numberand transmitted by the at least one relay node; and

a processing module, configured to order the data unit based on thenumber, where

the transceiver module is further configured to transmit a first dataunit group to the first device in order based on the number, where thefirst data unit group includes the ordered data unit.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

In the technical solution of this embodiment of this application, thefirst relay node can add numbers to data units or order data units,thereby avoiding a packet loss problem generated because a data unit isbeyond a receive window of a receive end, and improving accuracy of datatransmission and efficiency of data transmission.

With reference to the seventeenth aspect, in a first possibleimplementation of the seventeenth aspect, the number is added by anadaptation layer of the second device.

With reference to the seventeenth aspect, in a second possibleimplementation of the seventeenth aspect, an adaptation layer of thecommunications device has an ordering function; or

a radio link control RLC entity of the communications device has anordering function.

With reference to the second possible implementation of the seventeenthaspect, in a third possible implementation, the adaptation layer islocated above the radio link control RLC entity.

With reference to the second possible implementation of the seventeenthaspect, in a fourth possible implementation, the adaptation layer islocated above a media access control MAC entity.

According to an eighteenth aspect, a communications device is provided.A first device communicates with a second device by using at least onecommunications device, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver module, configured to receive a data unit transmitted by arelay node that is connected to the communications device, where thedata unit has a number; and

a processing module, configured to order the data unit having thenumber.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the second relay node, that is, the communicationsdevice may be an intermediate relay node.

In the technical solution of this embodiment of this application, thesecond relay node can order data units that have numbers, therebyavoiding a packet loss problem generated because a data unit is beyond areceive window of a receive end, and improving accuracy of datatransmission and efficiency of data transmission.

With reference to the eighteenth aspect, in a first possibleimplementation of the eighteenth aspect, the number is added by anadaptation layer of the second device; or

the number is added by a relay node that directly communicates with thesecond relay node.

With reference to the first possible implementation of the eighteenthaspect, in a second possible implementation, an adaptation layer of thecommunications device has an ordering function; or

a radio link control RLC entity of the communications device has anordering function.

With reference to the second possible implementation of the eighteenthaspect, in a third possible implementation, the adaptation layer islocated above the radio link control RLC entity.

With reference to the second possible implementation of the eighteenthaspect, in a fourth possible implementation, the adaptation layer islocated above a media access control MAC entity.

According to a nineteenth aspect, a communications device is provided.The communications device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver module, configured to receive a third message, where thethird message includes hop count information for communication betweenthe first device and the second device; and

a processing module, configured to determine a first sequence rangebased on the hop count information, where the first sequence range isused to indicate a range of sequence numbers allocated by the firstdevice.

In the technical solution of this embodiment of this application, amaximum quantity of data units that a transmit end is allowed totransmit is controlled, thereby avoiding a packet loss problem generatedbecause a data unit is beyond a receive window of a receive end, andimproving accuracy of data transmission and efficiency of datatransmission.

With reference to the nineteenth aspect, in a first possibleimplementation of the nineteenth aspect, the first sequence range isless than or equal to a quantity of allocated sequence numbers, and thequantity of allocated sequence numbers is a sequence number spacedivided by a hop count and then divided by 2.

With reference to the nineteenth aspect or the first possibleimplementation of the nineteenth aspect, in a second possibleimplementation, the third message is a broadcast message.

With reference to the nineteenth aspect or the first possibleimplementation of the nineteenth aspect, in a third possibleimplementation, the third message is a message transmitted by usingdedicated signaling.

With reference to the nineteenth aspect, or the first, the second, orthe third possible implementation of the nineteenth aspect, in a fourthpossible implementation, the third message is transmitted by the seconddevice.

With reference to the nineteenth aspect, or the first, the second, orthe third possible implementation of the nineteenth aspect, in a fifthpossible implementation, the third message is transmitted by the atleast one relay node.

According to a twentieth aspect, a communications device is provided. Afirst device communicates with a second device by using at least onecommunications device, and the at least one communications device doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a processing module, configured to determine first hop countinformation, where the communications module is a relay node thatdirectly communicates with the first device; and

a transceiver module, configured to transmit a third message to thefirst device, where the third message includes the first hop countinformation, where

the first hop count information is a quantity of the at least onecommunications device or a quantity of the at least one communicationsdevice plus 1.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

In the technical solution of this embodiment of this application, aquantity of data units at a transmit end is controlled, thereby avoidinga packet loss problem generated because a data unit is beyond a receivewindow of a receive end, and improving accuracy of data transmission andefficiency of data transmission.

With reference to the twentieth aspect, in a first possibleimplementation of the twentieth aspect, the transceiver module isfurther configured to:

transmit the third message to the first device by broadcast.

With reference to the twentieth aspect, in a second possibleimplementation of the twentieth aspect, the transceiver module isfurther configured to:

transmit the third message to the first device by using dedicatedsignaling.

With reference to the twentieth aspect, in a third possibleimplementation of the twentieth aspect, the processing module is furtherconfigured to:

obtain the first hop count information by adding 1 to second hop countinformation broadcast by a previous-hop relay node of the communicationsdevice.

According to a twenty-first aspect, a communications device is provided.The communications device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver module, configured to receive, by using the at least onerelay node, a first data unit transmitted by the second device, wherethe first data unit carries a count value; and

a processing module, configured to process the first data unit based onthe count value carried in the first data unit.

In the technical solution of this embodiment of this application, amaximum edge of a transmit window exists at a transmit end, a maximumedge of a receive window does not exist at a receive end, and a dataunit carrying a count value is transmitted, so that the data unit isprocessed, thereby avoiding a packet loss problem generated because adata unit is beyond the receive window of the receive end, and improvingaccuracy of data transmission and efficiency of data transmission.

With reference to the twenty-first aspect, in a first possibleimplementation of the twenty-first aspect, the processing module isfurther configured to:

if the count value of the first data unit is greater than a count valuenext to a count value of a last data unit currently already delivered,store the first data unit; or

if the count value of the first data unit is equal to a count value nextto a count value of a last data unit currently already delivered,deliver the first data unit to an upper layer of a packet dataconvergence protocol PDCP entity; or

if the count value of the first data unit is less than a count valuenext to a count value of a last data unit currently already delivered,discard the first data unit.

With reference to the first possible implementation of the twenty-firstaspect, in a second possible implementation, the communications devicefurther includes:

a storage module, configured to store the first data unit, and deliverthe first data unit to the upper layer of the PDCP entity in order basedon the count value of the first data unit.

With reference to the twenty-first aspect, or the first or the secondpossible implementation of the twenty-first aspect, in a third possibleimplementation, the first data unit is in the first sequence range.

With reference to the third possible implementation of the twenty-firstaspect, in a fourth possible implementation, the first sequence rangeindicates a range of count values that the second device is allowed toallocate or a range of count values that the second device is allowed toallocate when transmitting the first data unit.

With reference to the third or the fourth possible implementation of thetwenty-first aspect, in a fifth possible implementation, a size of thefirst sequence range is half of a sequence number space or less thanhalf of a sequence number space.

According to a twenty-second aspect, a communications device isprovided. A first device communicates with the communications device byusing at least one relay node, and the at least one relay node does nothave a packet data convergence protocol PDCP entity. The communicationsdevice includes:

a transceiver module, configured to transmit a first data unit to thefirst device by using the at least one relay node, where the first dataunit carries a count value, where

the first data unit belongs to a first sequence range, and the firstsequence range is used to indicate a range of count values that thesecond device is allowed to allocate.

With reference to the twenty-second aspect, in a first possibleimplementation of the twenty-second aspect, a size of the first sequencerange is half of a sequence number space or less than half of a sequencenumber space.

According to a twenty-third aspect, a communications device is provided.The communications device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver, configured to transmit a first data unit group, where thefirst data unit group is in a first sequence range, where

the transceiver is further configured to receive first information byusing the at least one relay node, where the first information is usedto indicate a data unit that the second device has received and/or hasnot received in the first data unit group; and

a processor, configured to determine a second sequence range based onthe first information.

With reference to the twenty-third aspect, in a first possibleimplementation of the twenty-third aspect, the processor is furtherconfigured to:

if the first information includes information about successful receptionof N consecutive data units starting from the first data unit in thefirst sequence range, obtain the second sequence range by shifting thefirst sequence range by N sequences, where N is a positive integer.

With reference to the twenty-third aspect or the first possibleimplementation of the twenty-third aspect, in a second possibleimplementation, the transceiver is further configured to:

receive a first message transmitted by the second device and forwardedby the at least one relay node, where the first message includes thefirst information.

With reference to the second possible implementation of the twenty-thirdaspect, in a third possible implementation, the first message is astatus report of a PDCP entity; or

the first message is a status report of a radio link control RLC entity.

With reference to the twenty-third aspect or the first possibleimplementation of the twenty-third aspect, in a fourth possibleimplementation, the transceiver is further configured to receive asecond message obtained by the at least one relay node based on a firstmessage transmitted by the second device, where the second messageincludes the first information.

With reference to the fourth possible implementation of the twenty-thirdaspect, in a fifth possible implementation, the second message isdetermined by the at least one relay node based on the first message anda mapping relationship between numbers of data units transmitted andreceived that is maintained by the at least one relay node.

With reference to the fifth possible implementation of the twenty-thirdaspect, in a sixth possible implementation, the second message is astatus report of an RLC entity.

With reference to the second or the third possible implementation of thetwenty-third aspect, in a seventh possible implementation, the firstmessage is a periodically transmitted message.

With reference to the second possible implementation of the twenty-thirdaspect, in an eighth possible implementation, the transceiver is furtherconfigured to transmit a query request to the second device.

According to a twenty-fourth aspect, a communications device isprovided. A first device communicates with a second device by using atleast one communications device, and the at least one communicationsdevice does not have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver, configured to receive first information transmitted by aprevious-hop relay node of the first relay node or the second device,where the first information is used to indicate a data unit that thesecond device has received and/or has not received in a first data unitgroup, and the first data unit group is in a first sequence range, where

the transceiver is further configured to forward the first information.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

According to a twenty-fourth aspect, a communications device isprovided. A first device communicates with a second device by using atleast one communications device, and the at least one communicationsdevice does not have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver, configured to receive first information transmitted bythe second device, where the first information is used to indicate adata unit that the second device has received and/or has not received ina first data unit group, and the first data unit group is in a firstsequence range; and

a processor, configured to generate a second message, where the secondinformation is determined based on a mapping relationship betweennumbers of data units transmitted and received that is maintained by thecommunications device and the first information, where

the transceiver is further configured to transmit the secondinformation.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

According to a twenty-fourth aspect, a communications device isprovided. A first device communicates with a second device by using atleast one communications device, and the at least one communicationsdevice does not have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver, configured to receive a first data unit group transmittedby the first device; and

a processor, configured to add numbers to data units in the first dataunit group.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

With reference to the twenty-fourth aspect, in a first possibleimplementation of the twenty-fourth aspect, the processor is furtherconfigured to add numbers to data units in the first data unit groupbased on receiving order.

With reference to the twenty-fourth aspect or the first possibleimplementation of the twenty-fourth aspect, in a second possibleimplementation, the processor is further configured to order the dataunits in the first data unit group.

With reference to the twenty-fourth aspect, or the first or the secondpossible implementation of the twenty-fourth aspect, in a third possibleimplementation, an adaptation layer of the communications device has anordering function; or

a radio link control RLC entity of the communications device has anordering function; and/or

the adaptation layer of the communications device has a numberingfunction.

With reference to the third possible implementation of the twenty-fourthaspect, in a fourth possible implementation, the adaptation layer islocated above the radio link control RLC entity.

With reference to the third possible implementation of the twenty-fourthaspect, in a fifth possible implementation, the adaptation layer islocated above a media access control MAC entity.

According to a twenty-fifth aspect, a communications device is provided.A first device communicates with a second device by using at least onecommunications device, and the at least one communications device doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver, configured to receive a data unit transmitted by a relaynode that is connected to the communications device, where the data unithas a number; and

a processor, configured to order the data unit having the number.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the second relay node, that is, the communicationsdevice may be an intermediate relay node.

With reference to the twenty-fifth aspect, in a first possibleimplementation of the twenty-fifth aspect, the number is added by afirst relay node, and the first relay node is a relay node that directlycommunicates with the first device; or

the number is added by a relay node that directly communicates with thecommunications device.

With reference to the first possible implementation of the twenty-fifthaspect, in a second possible implementation, an adaptation layer of thefirst relay node has an ordering function; or

a radio link control RLC entity of the first relay node has an orderingfunction; and/or

the adaptation layer of the first relay node has a numbering function.

With reference to the twenty-fifth aspect or the first possibleimplementation of the twenty-fifth aspect, in a third possibleimplementation, an adaptation layer of the communications device has anordering function; or

a radio link control RLC entity of the communications device has anordering function.

With reference to the second or the third possible implementation of thetwenty-fifth aspect, in a fourth possible implementation, the adaptationlayer is located above the radio link control RLC entity.

With reference to the second or the third possible implementation of thetwenty-fifth aspect, in a fifth possible implementation, the adaptationlayer is located above a media access control MAC entity.

According to a twenty-sixth aspect, a communications device is provided.The communications device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver, configured to receive a third message, where the thirdmessage includes hop count information for communication between thefirst device and the second device; and

a processor, configured to determine a first sequence range based on thehop count information, where the first sequence range is used toindicate a range of sequence numbers allocated by the first device.

In the technical solution of this embodiment of this application, amaximum quantity of data units that a transmit end is allowed totransmit is controlled, thereby avoiding a packet loss problem generatedbecause a data unit is beyond a receive window of a receive end, andimproving accuracy of data transmission and efficiency of datatransmission.

With reference to the twenty-sixth aspect, in a first possibleimplementation of the twenty-sixth aspect, the first sequence range isless than or equal to a quantity of allocated sequence numbers, and thequantity of allocated sequence numbers is a sequence number spacedivided by a hop count and then divided by 2.

With reference to the twenty-sixth aspect or the first possibleimplementation of the twenty-sixth aspect, in a second possibleimplementation, the third message is a broadcast message.

With reference to the twenty-sixth aspect or the first possibleimplementation of the twenty-sixth aspect, in a third possibleimplementation, the third message is a message transmitted by usingdedicated signaling.

With reference to the twenty-sixth aspect, or the first, the second, orthe third possible implementation of the twenty-sixth aspect, in afourth possible implementation, the third message is transmitted by thesecond device.

With reference to the twenty-sixth aspect, or the first, the second, orthe third possible implementation of the twenty-sixth aspect, in a fifthpossible implementation, the third message is transmitted by the atleast one relay node.

According to a twenty-seventh aspect, a communications device isprovided. A first device communicates with a second device by using atleast one communications device, and the at least one relay node doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver, configured to receive a data unit having a number andtransmitted by the at least one relay node; and

a processor, configured to order the data unit based on the number,where

the transceiver is further configured to transmit a first data unitgroup to the first device in order based on the number, where the firstdata unit group includes the ordered data unit.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

In the technical solution of this embodiment of this application, thefirst relay node can add numbers to data units or order data units,thereby avoiding a packet loss problem generated because a data unit isbeyond a receive window of a receive end, and improving accuracy of datatransmission and efficiency of data transmission.

With reference to the twenty-seventh aspect, in a first possibleimplementation of the twenty-seventh aspect, the number is added by anadaptation layer of the second device.

With reference to the twenty-seventh aspect, in a second possibleimplementation of the twenty-seventh aspect, an adaptation layer of thecommunications device has an ordering function; or

a radio link control RLC entity of the communications device has anordering function.

With reference to the second possible implementation of thetwenty-seventh aspect, in a third possible implementation, theadaptation layer is located above the radio link control RLC entity.

With reference to the second possible implementation of thetwenty-seventh aspect, in a fourth possible implementation, theadaptation layer is located above a media access control MAC entity.

According to a twenty-eighth aspect, a communications device isprovided. A first device communicates with a second device by using atleast one communications device, and the at least one relay node doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a transceiver, configured to receive a data unit transmitted by a relaynode that is connected to the communications device, where the data unithas a number; and

a processor, configured to order the data unit having the number.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the second relay node, that is, the communicationsdevice may be an intermediate relay node.

In the technical solution of this embodiment of this application, thesecond relay node can order data units that have numbers, therebyavoiding a packet loss problem generated because a data unit is beyond areceive window of a receive end, and improving accuracy of datatransmission and efficiency of data transmission.

With reference to the twenty-eighth aspect, in a first possibleimplementation of the twenty-eighth aspect, the number is added by anadaptation layer of the second device; or

the number is added by a relay node that directly communicates with thesecond relay node.

With reference to the first possible implementation of the twenty-eighthaspect, in a second possible implementation, an adaptation layer of thecommunications device has an ordering function; or

a radio link control RLC entity of the communications device has anordering function.

With reference to the second possible implementation of thetwenty-eighth aspect, in a third possible implementation, the adaptationlayer is located above the radio link control RLC entity.

With reference to the second possible implementation of thetwenty-eighth aspect, in a fourth possible implementation, theadaptation layer is located above a media access control MAC entity.

According to a twenty-ninth aspect, a communications device is provided.A first device communicates with a second device by using at least onecommunications device, and the at least one communications device doesnot have a packet data convergence protocol PDCP entity. Thecommunications device includes:

a processor, configured to determine first hop count information, wherethe communications device is a relay node that directly communicateswith the first device; and

a transceiver, configured to transmit a third message to the firstdevice, where the third message includes the first hop countinformation, where

the first hop count information is a quantity of the at least onecommunications device or a quantity of the at least one communicationsdevice plus 1.

It should be noted that the communications device in this embodiment ofthis application may correspond to the relay node in the foregoingmethod, for example, the first relay node.

In the technical solution of this embodiment of this application, aquantity of data units at a transmit end is controlled, thereby avoidinga packet loss problem generated because a data unit is beyond a receivewindow of a receive end, and improving accuracy of data transmission andefficiency of data transmission.

With reference to the twenty-ninth aspect, in a first possibleimplementation of the twenty-ninth aspect, the transceiver is furtherconfigured to:

transmit the third message to the first device by broadcast.

With reference to the twenty-ninth aspect, in a second possibleimplementation of the twenty-ninth aspect, the transceiver is furtherconfigured to:

transmit the third message to the first device by using dedicatedsignaling.

With reference to the twenty-ninth aspect, in a third possibleimplementation of the twenty-ninth aspect, the processor is furtherconfigured to:

obtain the first hop count information by adding 1 to second hop countinformation broadcast by a previous-hop relay node of the communicationsdevice.

According to a thirtieth aspect, a communications device is provided.The communications device communicates with a second device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver, configured to receive, by using the at least one relaynode, a first data unit transmitted by the second device, where thefirst data unit carries a count value; and

a processor, configured to process the first data unit based on thecount value carried in the first data unit.

In the technical solution of this embodiment of this application, amaximum edge of a transmit window exists at a transmit end, a maximumedge of a receive window does not exist at a receive end, and a dataunit carrying a count value is transmitted, so that the data unit isprocessed, thereby avoiding a packet loss problem generated because adata unit is beyond the receive window of the receive end, and improvingaccuracy of data transmission and efficiency of data transmission.

With reference to the thirtieth aspect, in a first possibleimplementation of the thirtieth aspect, the processor is furtherconfigured to:

if the count value of the first data unit is greater than a count valuenext to a count value of a last data unit currently already delivered,store the first data unit; or

if the count value of the first data unit is equal to a count value nextto a count value of a last data unit currently already delivered,deliver the first data unit to an upper layer of a packet dataconvergence protocol PDCP entity; or

if the count value of the first data unit is less than a count valuenext to a count value of a last data unit currently already delivered,discard the first data unit.

With reference to the first possible implementation of the thirtiethaspect, in a second possible implementation, the communications devicefurther includes:

a memory, configured to store the first data unit, and deliver the firstdata unit to the upper layer of the PDCP entity in order based on thecount value of the first data unit.

With reference to the thirtieth aspect, or the first or the secondpossible implementation of the thirtieth aspect, in a third possibleimplementation, the first data unit is in the first sequence range.

With reference to the third possible implementation of the thirtiethaspect, in a fourth possible implementation, the first sequence rangeindicates a range of count values that the second device is allowed toallocate or a range of count values that the second device is allowed toallocate when transmitting the first data unit.

With reference to the third or the fourth possible implementation of thethirtieth aspect, in a fifth possible implementation, a size of thefirst sequence range is half of a sequence number space or less thanhalf of a sequence number space.

According to a thirty-first aspect, a communications device is provided.A first device communicates with the communications device by using atleast one relay node, and the at least one relay node does not have apacket data convergence protocol PDCP entity. The communications deviceincludes:

a transceiver, configured to transmit a first data unit to the firstdevice by using the at least one relay node, where the first data unitcarries a count value, where

the first data unit belongs to a first sequence range, and the firstsequence range is used to indicate a range of count values that thesecond device is allowed to allocate.

With reference to the thirty-first aspect, in a first possibleimplementation of the thirty-first aspect, a size of the first sequencerange is half of a sequence number space or less than half of a sequencenumber space.

According to a thirty-second aspect, a system-on-chip is provided andapplied to a communications device. The system-on-chip includes at leastone processor, at least one memory, and an interface circuit. Theinterface circuit is responsible for information exchange between thesystem-on-chip and the outside. The at least one memory, the interfacecircuit, and the at least one processor are interconnected by cables.The at least one memory stores an instruction, and the at least oneprocessor executes the instruction to perform an operation performed bythe communications device in the method in each of the foregoingaspects.

According to a thirty-third aspect, a communications system is providedand includes a communications device, where the communications device isthe communications device in each of the foregoing aspects.

According to a thirty-fourth aspect, a computer program product isprovided and applied to a communications device, where the computerprogram product includes a series of instructions, and when theinstruction is run, an operation performed by the communications devicein the method in each of the foregoing aspects is performed.

According to a thirty-fifth aspect, a computer-readable storage mediumis provided, where the computer-readable storage medium stores aninstruction, and when the instruction is run on a computer, the computeris enabled to perform the method in each of the foregoing aspects.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a communications system to which a dataprocessing method in this application is applicable,

FIG. 2 is a schematic structural diagram of a scenario 200 of a dataprocessing method according to an implementation of this application;

FIG. 3 is a schematic structural diagram of a count value (COUNT) of adata unit according to an embodiment of this application;

FIG. 4 is a schematic diagram of a data unit processing method accordingto an embodiment of this application;

FIG. 5 is a schematic diagram of a data unit processing method accordingto an embodiment of this application;

FIG. 6 is a schematic interaction flowchart of a data unit processingmethod according to an embodiment of this application;

FIG. 7 is a schematic interaction flowchart of a data unit processingmethod according to another embodiment of this application;

FIG. 8 is a schematic interaction flowchart of a data unit processingmethod according to another embodiment of this application;

FIG. 9 is a schematic diagram of a data unit processing method accordingto another embodiment of this application;

FIG. 10 is a schematic diagram of a data unit processing methodaccording to still another embodiment of this application;

FIG. 11 is a schematic diagram of a data unit processing methodaccording to still another embodiment of this application;

FIG. 12 is a schematic diagram of a data unit processing methodaccording to still another embodiment of this application;

FIG. 13 is a schematic interaction flowchart of a data unit processingmethod according to still another embodiment of this application;

FIG. 14 is a schematic interaction flowchart of a data unit processingmethod according to still another embodiment of this application;

FIG. 15 is a schematic diagram of a data unit processing methodaccording to still another embodiment of this application;

FIG. 16 is a schematic interaction flowchart of a data unit processingmethod according to still another embodiment of this application;

FIG. 17 is a schematic block diagram of a communications device 1200according to an embodiment of this application;

FIG. 18 is a schematic block diagram of a communications device 1300according to an embodiment of this application;

FIG. 19 is a schematic block diagram of a communications device 1400according to an embodiment of this application; and

FIG. 20 is a schematic block diagram of a communications device 1500according to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

In NR in a 5G system, the applicant finds that when a relay node is alayer 2 relay not including a PDCP layer, because an RLC layer of therelay node does not have a reordering function, further disorder iscaused at each hop on a basis of a previous hop during transmission in amulti-hop link. Consequently, when data processing is performed by userequipment and a donor base station in the multi-hop link in the 5Gsystem, a packet loss problem may be generated. This severely affectsaccuracy of data transmission, reduces communication efficiency, andcauses poor user experience. The solutions provided hereinafter canresolve the packet loss problem generated when data processing isperformed by the user equipment and the donor base station in themulti-hop link in the 5G system, improve accuracy of data transmissionand efficiency of data transmission, and improve user experience.

The following describes technical solutions of this application withreference to accompanying drawings.

The technical solutions of the embodiments of this application may beapplied to various communications systems, such as a global system formobile communications (Global System of Mobile Communication, GSM), acode division multiple access (Code Division Multiple Access, CDMA)system, a wideband code division multiple access (Wideband Code DivisionMultiple Access, WCDMA) system, a general packet radio service (GeneralPacket Radio Service, GPRS), a long term evolution (Long Term Evolution,LTE) system, an LTE frequency division duplex (Frequency DivisionDuplex, FDD) system, an LTE time division duplex (Time Division Duplex,TDD) system, a universal mobile telecommunications system (UniversalMobile Telecommunication System, UMTS), a worldwide interoperability formicrowave access (Worldwide Interoperability for Microwave Access,WiMAX) communications system, a future 5th generation (5th Generation,5G) system, or a new radio (New Radio, NR) system.

A terminal device in the embodiments of this application may be userequipment, an access terminal, a subscriber unit, a subscriber station,a mobile station, a mobile console, a remote station, a remote terminal,a mobile device, a user terminal, a terminal, a wireless communicationsdevice, a user agent, a user apparatus, or the like. The terminal devicemay alternatively be a cellular phone, a cordless phone, a sessioninitiation protocol (Session Initiation Protocol, SIP) phone, a wirelesslocal loop (Wireless Local Loop, WLL) station, a personal digitalassistant (Personal Digital Assistant, PDA), a handheld device having awireless communication function, a computing device, another processingdevice connected to a wireless modem, a vehicle-mounted device, awearable device, a terminal device in a future 5G network, or a terminaldevice in a future evolved public land mobile network (Public LandMobile Network, PLMN). This is not limited in the embodiments of thisapplication.

A network device in the embodiments of this application may be a devicefor communicating with a terminal device. The network device may be abase transceiver station (Base Transceiver Station, BTS) in a globalsystem for mobile communications (Global System of Mobile communication,GSM) system or a code division multiple access (Code Division MultipleAccess, CDMA) system, or may be a NodeB (NodeB, NB) in a wideband codedivision multiple access (Wideband Code Division Multiple Access, WCDMA)system, or may be an evolved NodeB (Evolutional NodeB, eNB or eNodeB) inan LTE system, or may be a radio controller in a cloud radio accessnetwork (Cloud Radio Access Network, CRAN) scenario; or the networkdevice may be a relay station, an access point, an in-vehicle device, awearable device, a network device in a future 5G network, a networkdevice in a future evolved PLMN network, or the like. This is notlimited in the embodiments of this application.

FIG. 1 is a schematic diagram of a communications system to which acommunication method in this application is applicable. As shown in FIG.1 , the communications system 100 includes a network device 102, wherethe network device 102 may include a plurality of antennas, for example,antennas 104, 106, 108, 110, 112 and 114. In addition, the networkdevice 102 may additionally include a transmitter chain and a receiverchain. A person of ordinary skill in the art may understand that boththe transmitter chain and the receiver chain may include a plurality ofcomponents (for example, processors, modulators, multiplexers, encoders,demultiplexers, or antennas) related to signal transmission andreception.

The network device 102 may communicate with a plurality of terminaldevices (for example, a terminal device 116 and a terminal device 122).However, it may be understood that the network device 102 cancommunicate with any quantity of terminal devices similar to theterminal device 116 or 122. The terminal devices 116 and 122 may be, forexample, cellular phones, smartphones, portable computers, handheldcommunications devices, handheld computing devices, satellite radioapparatuses, global positioning systems, PDAs, and/or any otherappropriate devices used for communication in the wirelesscommunications system 100.

As shown in FIG. 1 , the terminal device 116 communicates with theantennas 112 and 114, where the antennas 112 and 114 transmitinformation to the terminal device 116 through a forward link 118, andreceive information from the terminal device 116 through a reverse link120. In addition, the terminal device 122 communicates with the antennas104 and 106, where the antennas 104 and 106 transmit information to theterminal device 122 through a forward link 124, and receive informationfrom the terminal device 122 through a reverse link 126.

For example, in an FDD system, for example, the forward link 118 may usea frequency band different from that used by the reverse link 120, andthe forward link 124 may use a frequency band different from that usedby the reverse link 126.

For another example, in a TDD system and a full duplex (full duplex)system, the forward link 118 and the reverse link 120 may use a samefrequency band, and the forward link 124 and the reverse link 126 mayuse a same frequency band.

Each antenna (or an antenna group including a plurality of antennas)and/or an area designed for communication is referred to as a sector ofthe network device 102. For example, the antenna group may be designedto communicate with a terminal device in a sector of a coverage area ofthe network device 102. In a process in which the network device 102communicates with the terminal devices 116 and 122 through the forwardlinks 118 and 124 respectively, transmit antennas of the network device102 may use beamforming to improve signal-to-noise ratios of the forwardlinks 118 and 124. In addition, in contrast to a manner in which anetwork device uses a single antenna to transmit signals to all terminaldevices served by the network device, when the network device 102 usesbeamforming to transmit signals to the terminal devices 116 and 122 thatare distributed randomly in a related coverage area, mobile devices in aneighboring cell receive less interference.

At a given time, the network device 102, the terminal device 116, or theterminal device 122 may be a wireless communications transmittingapparatus and/or a wireless communications receiving apparatus. Whentransmitting data, the wireless communications transmitting apparatusmay encode data for transmission. Specifically, the wirelesscommunications transmitting apparatus may obtain (for example, generate,receive from another communications apparatus, or store in a memory) aquantity of data bits that need to be transmitted to the wirelesscommunications receiving apparatus through a channel. Such data bits maybe included in a transport block (or a plurality of transport blocks) ofdata, and the transport block may be segmented to generate a pluralityof code blocks.

In addition, the communications system 100 may be a PLMN network or adevice-to-device (device-to-device, D2D) network or a machine to machine(machine to machine, M2M) network or another network. FIG. 1 is merely asimplified schematic diagram of an example, and the network may furtherinclude other network devices not shown in FIG. 1 .

FIG. 2 is a schematic diagram of a system 200 to which a communicationmethod according to an embodiment of this application is applicable.FIG. 2 is a structural diagram of a possible IAB network in 5G. Thesystem 200 includes access network devices. The access network devicesinclude a donor base station (Donor 5G NodeB, DgNB) 210 and one or morerelay nodes (Relay Node, RN), for example, a relay node 201, a relaynode 102, and a relay node 203. An access network device may communicatewith a plurality of terminal devices (for example, a terminal device 221and a terminal device 222).

In the structural diagram of the IAB network shown in FIG. 2 , thenetwork structure supports an integrated access and backhaul technologybased on a 5G new radio technology. In FIG. 2 , the donor base stationmay be directly connected to a core network. For example, a plurality ofrelay nodes may be connected to the donor base station, and one relaynode may be connected to another relay node. Herein, the relay node maybe a base station. Paths between base stations, for example, a pathbetween the donor base station and a relay node and a path between relaynodes, may be all referred to as backhaul paths. A terminal device maybe connected to the donor base station or a relay node. A directconnection between the terminal device and the donor base station is aone-hop path. The terminal device may be further connected to the donorbase station by using one or more relay nodes. In this case, theconnection is a multi-hop path. Paths between terminal devices and basestations, for example, a path between the donor base station and aterminal device and a path between a relay node and a terminal device,may be all referred to as access paths.

It should be noted that in an application scenario shown in FIG. 2 , aterminal device may communicate with the donor base station by using aplurality of relay nodes. On one hand, a relay node may provide largenetwork coverage to reduce communication costs; on the other hand, acommunication method for wireless transmission is provided by using therelay node.

It should be understood that FIG. 2 is merely a simplified schematicdiagram of an example, and the network may further include other accessnetwork devices not shown in FIG. 2 .

When data units are transmitted over an air interface of a 5G system,although the data units (service data units) are transmitted over an airinterface of a transmit end (transmitting device) in order, reception ata receive end (receiving device) may be disordered due to parallelrunning of a plurality of HARQ processes. Sequence numbers (SequenceNumber, SN) are added to the data units at a PDCP layer of the transmitend. A receiving PDCP entity performs reordering and duplicate detectionby using the SNs, to ensure that the data units are delivered in orderand that duplicate units are detected. The transmit end and the receiveend further need to maintain a same hyper frame number (Hyper FrameNumber, HFN). A purpose of using the HFN is to reduce a quantity of bitstransmitted over the air interface, that is, only a sequence numberneeds to be transmitted. An SN and an HFN constitute a count (COUNT)value of a data unit. Each data unit has a count value. Transmission isperformed over the air interface of the transmit end (transmittingdevice) in ascending order of count values of the data units. Thetransmit end needs to maintain a quantity of transmitted SNs so that itdoes not exceed half of a total quantity of SNs, to avoid disorder offrame numbers. Likewise, the receive end also uses a length of half of aquantity of SNs as a receive window. At the receive end, received dataunits may also be disordered. However, because a quantity of data unitstransmitted by the transmit end over the air interface does not exceedhalf of the quantity of SNs, the received data units are generallydisordered when delivered to the PDCP layer. Although the data units aredisordered, the data units are in the receive window. The PDCP layerorders the data units in the receive window based on the count values,and delivers the data units to an upper layer in order of the countvalues.

FIG. 3 is a schematic structural diagram of a count (COUNT) value of adata unit. As can be learned from FIG. 3 , the count value of the dataunit includes an SN field and an HFN field, where a sum of a quantity ofbits (bit) of the HFN field part and a quantity of bits (bit) of the SNfield part is 32 bits, that is, a COUNT field in the data unit is 32bits.

In 5G NR, a PDCP entity of the receiving device reorders the receiveddata units based on the count values of the data units (service dataunits). The ordering and delivering process of the data units is asfollows:

after receiving a data unit, first inferring a currently received countvalue based on an SN number of the data unit and a maintained HFN;

determining whether the count value of the received data unit is in avalid receive window, that is, whether the count value is greater thanor equal to a next to-be-delivered count value; and if the count valueis not in the valid receive window, discarding the received data unit;or if the count value is in the valid receive window, storing the validdata unit in a PDCP layer, and then delivering the data units in order.

FIG. 4 is a schematic flowchart of a data unit processing method in theprior art. The data unit processing method in FIG. 3 may be applied tothe communications system shown in FIG. 2 .

It should be noted that for data to be transmitted in acknowledged mode(AM DRB), a range of sequence numbers to be transmitted is controlled byfeedback of an RLC layer. This is a visual method for controllingtransmission of data of not more than half of SNs; for data to betransmitted in unacknowledged mode (UM DRB), a range of sequence numbersto be transmitted may be controlled by feedback of a HARQ process ofMAC, so that data of not more than half of SNs is transmitted.

In a scenario f a multi-hop link of IAB, because a multi-hop linkexists, disordered transmission of data units may occur. As shown inFIG. 4 , a terminal device transmits data units whose sequence numbersare 1 to N in a transmit window, where the transmit window is a range ofsequence numbers that a transmit end can transmit currently. Due todisorder on an air interface, a first relay node receives disordereddata units. For example, as shown in FIG. 4 , in a possible case, thefirst relay node may successfully receive a data unit numbered N+1 afterreceiving a data unit numbered 1 that is transmitted by the transmitend, but data units numbered 2 to N are all in a retransmitted state.

Data units received in disorder at the first hop continue to betransmitted in receiving order, that is, in disorder. For example, thedisordered data units received by the relay node 1 continue to betransmitted to a relay node 2. However, the transmit end determines,based on feedback about the data units received at the first hop, arange of allocated sequence numbers, which is referred to as a “transmitwindow”. To be specific, more data may be transmitted by the transmitend to the first-hop node. Consequently, data units (for example, thedata units whose sequence numbers are 1 to N) in a receive window anddata units (for example, other data units than the data units whosesequence numbers are 1 to N) beyond the receive window are transmittedsimultaneously over the air interface. Because transmission over an airinterface at a second hop is still disordered, data in the receivewindow may arrive at a receive end earlier than data beyond the receivewindow. Consequently, data units received by the receive end are beyondthe receive window, and the receive end discards the data units.

It should be noted that in a transmission process of a data unit, thereceive end can recognize only a data unit in the receive windowcorresponding to the transmit window of the transmit end, and a dataunit beyond the receive window may be recognized by the receive end asexpired data. Therefore, a case of incorrectly considering that the dataunit has been received and discarding the data unit may occur. Forexample, if sequence numbers of corresponding data units in the transmitwindow are 1 to N, the receive end can recognize the data units whosesequence numbers are 1 to N in the receive window, but other data unitsthan the data units whose sequence numbers are 1 to N are discardedbecause the other data units are considered as data units alreadyreceived in a previous round.

Uplink data transmission in acknowledged mode (Acknowledge Mode, AM) isshown in FIG. 4 . Assuming that all transmitted PDCP SNs are 2N numericvalues, N PDCP data units may be transmitted simultaneously over the airinterface at a time. In this case, no data packet falls beyond thewindow due to disorder on the air interface at the first-hop receiveend. When receiving feedback about the data unit numbered 1 from thefirst-hop receive end, the transmit end may transmit the data unitnumbered N+1.

Considering a possible case of reception, after receiving the data unitnumbered 1, the first-hop receive end (relay node 1) first receives thedata unit numbered N+1 that is transmitted by the transmit end, and thenreceives a data unit numbered 2. Because an RLC layer in a 5G systemdoes not have a reordering function any longer, a PDCP layer in alayer-2 protocol stack is responsible for reordering received disordereddata units. However, a relay node does not have a PDCP layer andtherefore cannot perform reordering. The relay node 1 transmits (1, N+1,2, N . . . ) in order of currently received data units. During receptionat a second-hop receive end (relay node 2), the PDCP data unit numberedN+1 may be first received due to disorder, and receiving order may be(N+1, 1, N, 2 . . . ). When the data units are transmitted to a donorbase station, order of receiving the data units may be (N+1, 1, N, 2 . .. ). Because numbers 1 to N are currently in the receive window, thedata unit numbered N+1 is directly considered as being beyond thereceive window and is discarded.

Uplink data transmission in unacknowledged mode (Unacknowledged Mode,UM) is shown in FIG. 5 . In UM mode, an RLC layer does not number a dataunit that is not segmented. Therefore, from a perspective of RLC, withrespect to data units delivered by an upper layer to RLC, an airinterface may transmit all the data units if air interface resourcespermit. However, because the data units on the air interface aredisordered and a size of a transmit window on an air interface betweenrelays is uncontrolled, plenty of data units beyond the window may belost when a receive end receives the data units.

According to the embodiments of this application, it can be ensured thatthe data unit in the receive window encounters no packet loss that iscaused when the data unit is beyond the receive window. The followingdescribes in detail the embodiments of this application with referenceto specific examples. It should be noted that the examples are merelyintended to help a person skilled in the art better understand theembodiments of this application, but are not intended to limit the scopeof the embodiments of this application.

It should be understood that an application scenario of this applicationmay be data processing performed by a terminal device and a donor basestation after an entire control plane between the terminal device andthe donor base station is established in a 5G system or a futurecommunications system.

FIG. 6 is a schematic flowchart of a communication method 500 accordingto an embodiment of this application. The communication method 500 maybe applied to an uplink transmission scenario in the scenario shown inFIG. 2 , or certainly may be applied to another communication scenario.This is not limited in this embodiment of this application. Thecommunication method 500 includes the following steps.

S510. A first device transmits a first data unit group, where the firstdata unit group is in a first sequence range. Herein, using an uplinktransmission scenario as an example, for example, the first device maybe a terminal device, and the second device may be a donor base station.

It should be noted that the first sequence range is a range of dataunits that the terminal device can transmit.

S520. The first device receives first information by using at least onerelay node, where the first information is used to indicate a data unitthat the second device has received and/or has not received in the firstdata unit group. For example, the terminal device receives firstinformation by using the at least one relay node, where the firstinformation is used to indicate a data unit that the donor base stationhas received and/or has not received in the first data unit group.

S530. The first device determines a second sequence range based on thefirst information. For example, the terminal device determines thesecond sequence range based on the first information.

In this embodiment of this application, the first device may transmitdata units in the first sequence range, and the first device determinesthe second sequence range based on the first information about the dataunit that the second device has received and/or has not received in thefirst data unit group, thereby avoiding a packet loss problem generatedbecause a data unit is beyond a receive window of a receive end, andimproving accuracy of data transmission and efficiency of datatransmission.

Optionally, in an embodiment of this application, that the first devicedetermines a second sequence range based on the first informationincludes:

if the first information includes information about successful receptionof N consecutive data units starting from the first data unit in thefirst sequence range, the first device obtains the second sequence rangeby shifting the first sequence range by N sequences, where N is apositive integer.

For example, the first sequence range may be a transmit window of theterminal device, and the first sequence range is data units whosesequence numbers are 1 to 10. The first data unit group may be dataunits numbered 1 to 10. When the first information includes informationabout successful reception of the data unit numbered 1 and the data unitnumbered 2 by the second device, it is determined, by shifting the firstsequence range by two sequences, that the second sequence range isnumber 3 to number 13.

It should be noted that when the first information includes informationabout successful reception of the data unit numbered 1 and the data unitnumbered 5 by the donor base station, it is determined, by shifting thefirst sequence range by one sequence, that the second sequence range isnumber 2 to number 11. If the first information includes informationabout successful reception of a data packet numbered 2 and a data packetnumbered 3 by the donor base station, the first sequence range is notshifted. It should be understood that when the first informationincludes information about successful reception of N consecutive dataunits starting from the first data unit by the donor base station, thatis, when information about successful reception of N consecutive dataunits starting from the data unit numbered 1 is received, the secondsequence is determined by shifting the first sequence range by Nsequences.

It should be understood that the first sequence range may be thetransmit window of the terminal device, and the transmit window may beless than or equal to half of an SN space.

It should be understood that the first sequence range is a sequencenumber range of data units that the terminal device can transmit, and arange of sequence numbers transmitted by the terminal device should bein the first sequence range. After the second sequence range isdetermined, sequence numbers transmitted by the terminal device shouldbe in the second sequence range. Optionally, in an embodiment of thisapplication, a first message received by the first device may be amessage transmitted by the second device, and the first device receives,from the second device, the first message forwarded by the at least onerelay node.

For example, the terminal device receives a first message transmitted bythe donor base station and forwarded by the at least one relay node,where the first message includes the first information used to indicatethe data unit that the donor base station has received and/or has notreceived in the first data unit group.

For example, the first data unit group includes a data unit a, a dataunit b, a data unit c, a data unit d, and a data unit e, where sequencenumbers of the five data units may be numbers 1 to 5. The terminaldevice transmits the first data unit group to the donor base station byusing the at least one relay node. The donor base station receives dataunits numbered 1 to 3, but does not receive data units numbered 4 and 5.In this case, the donor base station transmits first information, wherethe first information includes information about the data units numbered1 to 3 that the donor base station has received and the data unitsnumbered 4 and 5 that the donor base station has not received. The donorbase station transmits a first message to the at least one relay node,and the at least one relay node forwards the first message to forwardthe first message to the terminal device, where the first messageincludes the first information.

It should be understood that in this embodiment, the at least one relaynode merely forwards the first message transmitted by the donor basestation and finally transmits the first message to the terminal device,and the relay node does not process the first message.

Optionally, in an embodiment, a first relay node receives the firstinformation transmitted by a previous-hop relay node of the first relaynode or the second device, where the first information is used toindicate the data unit that the second device has received and/or hasnot received in the first data unit group, and the first data unit groupis in the first sequence range; and

the first relay node forwards the first information.

Optionally, the first message may be a status report of a PDCP entitythat is transmitted by the donor base station; or the first message maybe a status report of an RLC entity that is transmitted by the donorbase station.

In an embodiment of this application, the first message may be a messageperiodically transmitted by the donor base station to the terminaldevice.

In an embodiment of this application, the first message may be a messagetransmitted by the donor base station to the terminal device when theterminal device transmits a query request to the donor base station, forexample, when a status of receiving the first data unit group by thedonor base station is queried.

Optionally, in an embodiment of this application, the terminal devicereceives a second message obtained by the at least one relay node basedon the first message transmitted by the donor base station, where thesecond message includes the first information used to indicate the dataunit that the donor base station has received and/or has not received inthe first data unit group. The second message is determined by the atleast one relay node based on the first message and a mappingrelationship between numbers of data units transmitted and received thatis maintained by the at least one relay node.

In an example, it is assumed that the terminal device communicates withthe donor base station by using a relay node 1 and a relay node 2, thatis, terminal device-relay node 1-relay node 2-donor base station. Theterminal device transmits the five data units a, b, c, d, and e to thedonor base station. An RLC entity of the terminal device adds headers tothe five data units separately, where the headers include numbers a-1,b-2, c-3, d-4, and e-5. The terminal device first transmits the fivedata units to the relay node 1, and the relay node 1 maintains a mappingrelationship between numbers of data units transmitted and received.

For example, the mapping relationship maintained by the relay node 1 is1-6, 2-7, 3-8, 4-9, and 5-10. To be specific, the headers 1, 2, 3, 4,and 5 of the five data units a, b, c, d, and e are removed at the relaynode 1, and then new headers a-6, b-7, c-8, d-9, and e-10 are added tothe data units. Then the relay node 1 transmits the five data units tothe relay node 2, and the relay node 2 also maintains a mappingrelationship between numbers of data units transmitted and received.

For example, the mapping relationship maintained by the relay node 2 is6-11, 7-12, 8-13, 9-14, and 10-15. To be specific, the headers 6, 7, 8,9, and 10 of the five data units a, b, c, d, and e, which are added atthe relay node 1, are removed at the relay node 2, and then new headersa-11, b-12, c-13, d-14, and e-15 are added to the data units. The relaynode 2 transmits the five data units to the donor base station. Forexample, if the donor base station successfully receives data unitswhose headers are 11, 12, and 13, but does not successfully receive dataunits whose headers are 14 and 15, a PDCP layer of the donor basestation can recognize that data units whose headers 11, 12, and 13 areremoved are the data unit a, the data unit b, and the data unit c. Inthis case, the donor base station transmits a first message indicatingthat the donor base station has received the data unit a, the data unitb, and the data unit c but has not received the data units whose headersare 14 and 15. To be specific, the donor base station transmits thefirst message to the relay node 2, indicating that the donor basestation has successfully received the data units whose headers are 11,12, and 13 but has not received the data units whose headers are 14 and15. Based on the maintained mapping relationship between numbers of dataunits transmitted and received, that is, 6-11, 7-12, 8-13, 9-14, and10-15, the relay node 2 transmits, to a relay node, that is, transmits,to the relay node 1, a processed first message indicating that the donorbase station has successfully received data units whose headers are 6,7, and 8 but has not received data units whose headers are 9 and 10.Based on the maintained mapping relationship between numbers of dataunits transmitted and received, that is, 1-6, 2-7, 3-8, 4-9, and 5-10,the relay node 1 transmits, to a terminal, that is, transmits, to theterminal device, a second message obtained by processing the firstmessage, indicating that the donor base station has successfullyreceived data units whose headers are 1, 2, and 3 but has not receiveddata units whose headers are 4 and 5. After receiving the secondmessage, the terminal device can know that the donor base station hassuccessfully received the data unit a, the data unit b, and the dataunit c but has not received the data unit d and the data unit e. Thesecond message may be a status report of an RLC entity.

Optionally, in an embodiment, the first relay node receives the firstinformation transmitted by the second device, where the firstinformation is used to indicate the data unit that the second device hasreceived and/or has not received in the first data unit group, and thefirst data unit group is in the first sequence range; and

the first relay node transmits second information, where the secondinformation is determined based on the mapping relationship betweennumbers of data units transmitted and received that is maintained by thefirst relay node and the first information, and the second informationis used to indicate the data unit that the second device has receivedand/or has not received in the first data unit group.

It should be noted that the mapping relationships between numbers thatare maintained by the relay node 1 and the relay node 2 may be mappingrelationships between RLC entity numbers of data units received by therelay nodes and RLC entity numbers of data units transmitted by therelay nodes to next-hop relay nodes, that is, mapping relationshipsbetween numbers of data units received by the relay nodes and numbers ofdata units transmitted by the relay nodes.

It should be understood that in the description of the foregoingembodiment, in an uplink transmission scenario, the first device may bea terminal device, and the second device may be a donor base station. Ina downlink transmission scenario, the first device may be a donor basestation, and the second device may be a terminal device. This is notlimited in this application.

FIG. 7 is a schematic flowchart of a communication method 600 accordingto an embodiment of this application. The communication method 600 maybe applied to an uplink transmission scenario or a downlink transmissionscenario in the scenario shown in FIG. 2 , or certainly may be appliedto another communication scenario. This is not limited in thisapplication. Using uplink transmission as an example, the communicationmethod 600 includes the following steps.

S610. A first relay node receives a first data unit group transmitted bythe first device.

For example, in an uplink transmission scenario, the first relay nodereceives a first data unit group transmitted by a terminal device.

S620. The first relay node adds numbers to data units in the first dataunit group.

Optionally, in an embodiment of this application, that the first relaynode adds numbers to data units in the first data unit group includes:

the first relay node adds the numbers to the data units in the firstdata unit group based on receiving order.

Optionally, in an embodiment of this application, before the first relaynode adds numbers to data units in the first data unit group, the methodfurther includes:

the first relay node orders the data units in the first data unit group.

In this embodiment of this application, in the technical solution ofthis embodiment of this application, the first relay node can addnumbers to data units, thereby avoiding a packet loss problem generatedbecause a data unit is beyond a receive window of a receive end, andimproving accuracy of data transmission and efficiency of datatransmission.

It should be noted that the first relay node is a relay node thatdirectly communicates with the first device. For example, in an uplinktransmission scenario, the first relay node is a relay node that maydirectly communicate with the terminal device.

Optionally, in an embodiment, the first relay node may have an orderingfunction and a numbering function; or the first relay node may have anumbering function; or the first relay node has an ordering function.This is not limited in this application.

FIG. 8 is a schematic flowchart of a communication method 400 accordingto an embodiment of this application. The communication method 400 maybe applied to an uplink transmission scenario or a downlink transmissionscenario in the scenario shown in FIG. 2 , or certainly may be appliedto another communication scenario. This is not limited in thisapplication. Using downlink transmission as an example, thecommunication method 400 includes the following steps.

S410. A first relay node receives a data unit having a number andtransmitted by at least one relay node or a second device.

S420. The first relay node orders the data unit based on the number.

For example, in a downlink transmission scenario, a base stationcommunicates with a terminal device by using a third relay node, asecond relay node, and the first relay node. The third relay nodedirectly communicates with the base station. The third relay nodereceives a first data unit group transmitted by the base station andadds numbers to the first data unit group in receiving order. The thirdrelay node transmits the first data unit group having the numbers to thesecond relay node. After the second relay node receives the first dataunit group having the numbers, the second relay node may order the firstdata unit group; or the second relay node may not order the first dataunit group, but directly transmits the first data unit group having thenumbers to the first relay node; and the first relay node receives dataunits having numbers, and orders the data units based on the numbers.

S430. The first relay node transmits a first data unit group to thefirst device in order based on the number, where the first data unitgroup includes the ordered data unit.

In this embodiment of this application, in the technical solution ofthis embodiment of this application, the first relay node can addnumbers to data units, thereby avoiding a packet loss problem generatedbecause a data unit is beyond a receive window of a receive end, andimproving accuracy of data transmission and efficiency of datatransmission.

For example, in a downlink transmission scenario, the base stationcommunicates with the terminal device by using the third relay node, thesecond relay node, and the first relay node. The first relay nodereceives a data unit having a number and transmitted by the second relaynode. The first relay node orders the data unit based on the number, andtransmits a first data unit group to the terminal device in order basedon the number, where the first data unit group includes the ordered dataunit.

In an embodiment of this application, as shown in FIG. 9 , FIG. 9 is aschematic diagram of a data processing method according to an embodimentof this application.

A first device communicates with a second device by using at least onerelay node. For example, the first device may communicate with thesecond device by using a first relay node, a second relay node, and athird relay node. The first relay node is a relay node connected to thefirst device. In this embodiment of this application, the first relaynode has numbering and ordering functions.

For example, a terminal device transmits data units whose sequencenumbers are 1 to 5 to the first relay node, and order of the data unitsreceived by the first relay node is: data unit numbered 2, data unitnumbered 1, data unit numbered 3, data unit numbered 4, and data unitnumbered 5. The first relay node may number the received data units. Thefirst relay node may perform numbering based on order of receiving thedata units. For example, the first relay node adds {circle around (1)}to the data unit whose sequence number is 2, adds {circle around (2)} tothe data unit whose sequence number is 1, adds {circle around (3)} tothe data unit whose sequence number is 3, adds {circle around (4)} tothe data unit whose sequence number is 4, and adds {circle around (5)}to the data unit whose sequence number is 5. The first relay node mayadd the numbers of the data units to headers of the data units.

It should be understood that a sequence number of a data unit is anumber that a PDCP layer can recognize, but a relay node does not have aPDCP layer and therefore cannot recognize the number. The first relaynode adds numbers {circle around (1)}, {circle around (2)}, {circlearound (3)}, {circle around (4)}, and {circle around (5)} to the dataunits based on the receiving order. The numbers added by the first relaynode are numbers that the relay node can recognize.

As shown in FIG. 9 , the first relay node transmits a data unit having anumber to the second relay node. The second relay node may not performordering based on the added number of the data unit. The second relaynode transmits the data unit to the third relay node. The third relaynode transmits the data unit to the second device. After performingordering based on the added number, the second device delivers the dataunit to a PDCP layer of the second device, thereby ensuring that thedata unit received by the PDCP layer of the second device is not beyonda receive window. The PDCP layer of the second device then performsordering based on a number of the PDCP layer, thereby avoiding a packetloss phenomenon generated on the second device because a data unit isbeyond the receive window.

As shown in FIG. 9 , an adaptation layer of the first relay node mayhave ordering and numbering functions; or an adaptation layer of thefirst relay node may have an ordering function; or an adaptation layerof the first relay node may have a numbering function. This is notlimited in this application.

Optionally, an adaptation layer of the second relay node may have anordering function, or an RLC entity of the second relay node may have anordering function. This is not limited in this application.

Optionally, in this embodiment of this application, the adaptation layermay be located above the RLC entity; or the adaptation layer may belocated above a MAC entity.

FIG. 10 is a schematic diagram of a data processing method according toanother embodiment of this application. As shown in FIG. 10 , a firstdevice communicates with a second device by using at least one relaynode. For example, the first device may communicate with the seconddevice by using a first relay node, a second relay node, and a thirdrelay node. The first relay node is a relay node connected to the firstdevice. In this embodiment of this application, the first relay node hasa numbering function.

The first relay node transmits a data unit having a number to the secondrelay node. The second relay node may order the data unit based on thenumber, and then the second relay node may transmit the data unit havingthe number to the third relay node. The third relay node may order thedata unit based on the number. The third relay node transmits theordered data unit to the second device, thereby ensuring that the dataunit received by the second device is not beyond a receive window, andavoiding a packet loss phenomenon generated on the second device becausea data unit is beyond the receive window.

In an embodiment of this application, the second relay node receives adata unit transmitted by a relay node that is connected to the secondrelay node, where the data unit has a number; and the second relay nodeorders the data unit having the number.

FIG. 11 is a schematic diagram of a processing method according toanother embodiment of this application. In an embodiment, a first deviceis a terminal device. In an uplink transmission scenario, as shown inthe figure, an RLC layer of a relay node has an ordering function. FIG.11 is a schematic diagram of a data processing method according toanother embodiment of this application. In FIG. 11 , a first device maybe a terminal device, and a second device may be a base station.

According to the data processing method shown in FIG. 11 , an RLC layerof a relay node has an ordering function. A first relay node transmits adata unit having a number to a second relay node; the second relay nodeperforms ordering based on the number of the data unit, and transmitsthe ordered data unit to a third relay node; and the third relay nodeorders the data unit based on the number of the data unit, and transmitsthe ordered data unit to the base station.

It should be understood that a sequence number of a data unit is anumber that a PDCP layer can recognize, but a relay node does not have aPDCP layer and therefore cannot recognize a number of the PDCP layer. Areceiving RLC entity of the first relay node orders the received dataunit based on a number of an RLC layer, performs numbering at the RLClayer based on receiving order, and transmits the data unit to thesecond relay node. A receiving RLC entity of the third relay node ordersthe received data unit based on a number of an RLC layer, performsnumbering at the RLC layer based on receiving order, and transmits thedata unit to the second device. An RLC layer of the second devicedelivers the data unit to a PDCP layer after ordering the data unitbased on a number of the RLC layer.

Optionally, in an embodiment, a first device is a terminal device. In adownlink transmission scenario, as shown in the figure, an RLC layer ofa relay node has an ordering function. FIG. 12 is a schematic diagram ofa data processing method according to another embodiment of thisapplication. In FIG. 12 , a first device may be a terminal device, and asecond device may be a base station.

According to the data processing method shown in FIG. 12 , an RLC layerof a relay node has an ordering function. A third relay node receives adata unit transmitted by the base station, and numbers and orders thedata unit; the third relay node transmits the ordered data unit having anumber to a second relay node; the second relay node performs orderingbased on the number of the data unit, and transmits the ordered dataunit to a first relay node; and the first relay node orders the dataunit based on the number of the data unit, and transmits the ordereddata unit to the terminal device.

It should be understood that a sequence number of a data unit is anumber that a PDCP layer can recognize, but a relay node does not have aPDCP layer and therefore cannot recognize a number of the PDCP layer. Areceiving RLC entity of the third relay node orders the received dataunit based on a number of an RLC layer, performs numbering at the RLClayer based on receiving order, and transmits the data unit to thesecond relay node. A receiving RLC entity of the first relay node ordersthe received data unit based on a number of an RLC layer, performsnumbering at the RLC layer based on receiving order, and transmits thedata unit to the first device. An RLC layer of the first device performsordering based on a number of the RLC layer or delivers the data unit toa PDCP layer based on receiving order.

In the technical solution of this embodiment of this application, thesecond relay node can order data units that have numbers, therebyavoiding a packet loss problem generated because a data unit is beyond areceive window of a receive end, and improving accuracy of datatransmission and efficiency of data transmission.

FIG. 13 is a schematic flowchart of a communication method 700 accordingto an embodiment of this application. The communication method 700 maybe applied to an uplink transmission scenario in the scenario shown inFIG. 2 , or certainly may be applied to another communication scenario.This is not limited in this application. The communication method 700includes the following steps.

S710. The first device receives a third message, where the third messageincludes hop count information for communication between the firstdevice and the second device.

For example, a terminal device receives a third message, where the thirdmessage includes hop count information. If the terminal devicecommunicates with a donor base station by using one relay node, the hopcount information is two hops; or if the terminal device communicateswith a donor base station by using two relay nodes, the hop countinformation is three hops.

Optionally, the third message may be a broadcast message; or the thirdmessage may be a message transmitted by using dedicated signaling.

Optionally, the third message may be a message transmitted by the donorbase station to the terminal device and forwarded by a relay node; orthe third message may be a message transmitted by a relay node to theterminal device.

S720. The first device determines a first sequence range based on thethird message, where the first sequence range is used to indicate arange of sequence numbers allocated by the first device or used toindicate a maximum quantity of data units that are allowed to betransmitted.

For example, the terminal device determines the first sequence rangebased on the hop count information included in the third message. Thefirst sequence range may be a transmit window of the terminal device.The terminal device may transmit a data unit included in the firstsequence range. The first sequence range is less than or equal to aquantity of allocated sequence numbers, and the quantity of allocatedsequence numbers is a sequence number space divided by a hop count andthen divided by 2. The sequence number space (SN space) is a totalquantity of sequence numbers. For example, if a sequence number is 12bits, the sequence number space is 2¹².

For example, FIG. 15 is a schematic diagram of a data processing methodaccording to an embodiment of this application. In FIG. 15 , two hopsare used as an example for description.

A donor base station transmits a third message to a terminal device,where the third message may be a broadcast message or a dedicatedmessage, notifying a hop count from the terminal device to the donorbase station. The terminal device controls, based on a hop count X tothe donor base station, a quantity of allocated SNs not to exceed asequence number space (SN space) divided by the hop count (X) and thendivided by 2. At each hop for carried data units, a quantity of dataunits simultaneously transmitted over an air interface also needs to becontrolled not to exceed SN space/X/2.

Using two hops as an example, a length of a receive window of the donorbase station is 2N. It should be understood that the length of thereceive window is SN space/2, that is, the terminal device at a transmitend controls a quantity of SNs allocated to data units not to exceed2N/2=N. As shown in FIG. 15 , it can be ensured that a data unitreceived by PDCP of the donor base station at a receive end is notbeyond the receive window, thereby avoiding a packet loss phenomenongenerated on the donor base station because a data unit is beyond thereceive window.

In a possible implementation, the quantity of allocated SNs iscontrolled not to exceed sequence number space (SNspace)/2^(loop count(X))/2. It should be noted that in the descriptionof the foregoing embodiment, in an uplink transmission scenario, thefirst device may be a terminal device, and the second device may be adonor base station. In a downlink transmission scenario, the firstdevice may be a donor base station, and the second device may be aterminal device. This is not limited in this application.

In the technical solution of this embodiment of this application, amaximum quantity of data units that a transmit end is allowed totransmit is controlled, thereby avoiding a packet loss problem generatedbecause a data unit is beyond a receive window of a receive end, andimproving accuracy of data transmission and efficiency of datatransmission.

FIG. 14 is a schematic flowchart of a communication method 800 accordingto an embodiment of this application. The communication method 800 maybe applied to an uplink transmission scenario in the scenario shown inFIG. 2 , or certainly may be applied to another communication scenario.This is not limited in this application. The communication method 800includes the following steps.

S810. A first relay node determines first hop count information, wherethe first relay node is a relay node that directly communicates with thefirst device.

For example, the first device may be a terminal device, and a seconddevice may be a base station.

For example, the terminal device receives a third message, where thethird message includes hop count information. If the terminal devicecommunicates with a donor base station by using one relay node, the hopcount information is two hops; or if the terminal device communicateswith a donor base station by using two relay nodes, the hop countinformation is three hops.

Alternatively, if the terminal device communicates with a donor basestation by using one relay node, the hop count information is one hop,or if the terminal device communicates with a donor base station byusing two relay nodes, the hop count information is two hops.

Optionally, that a first relay node determines first hop countinformation includes;

the first relay node obtains a quantity of the at least one relay nodeby adding 1 to hop count information broadcast by a previous-hop relaynode of the first relay node.

For example, the first relay node is connected to a second relay node,and the hop count information broadcast by the second relay node andreceived by the first relay node is that the second relay node is twohops. In this case, the first relay node adds 1 to the hop countinformation broadcast by the second relay node, that is, the first relaynode is three hops.

Optionally, the third message may be a broadcast message; or the thirdmessage may be a message transmitted by using dedicated signaling.

Optionally, the third message may be a message transmitted by the donorbase station to the terminal device and forwarded by a relay node; orthe third message may be a message transmitted by a relay node to theterminal device.

S820. The first relay node transmits a third message to the firstdevice, where the third message includes the first hop countinformation, and the first hop count information is the quantity of theat least one relay node or the quantity of the at least one relay nodeplus 1.

Optionally, that the first relay node determines the first hop countinformation includes:

the first relay node obtains the first hop count information by adding 1to second hop count information broadcast by a previous-hop relay nodeof the first relay node.

For example, the terminal device determines a first sequence range basedon the first hop count information included in the third message. Thefirst sequence range may be a transmit window of the terminal device.The terminal device may transmit a data unit included in the firstsequence range.

The first sequence range is less than or equal to a quantity ofallocated sequence numbers, and the quantity of allocated sequencenumbers is a sequence number space divided by a hop count and thendivided by 2. The sequence number space (SN space) is a total quantityof sequence numbers. For example, if a sequence number is 12 bits, thesequence number space is 2¹².

For example, FIG. 15 is a schematic diagram of a data processing methodaccording to an embodiment of this application. In FIG. 15 , two hopsare used as an example for description.

A relay transmits a third message to a terminal device, where the thirdmessage may be a broadcast message or a dedicated message, notifying ahop count from the terminal device to a donor base station. The terminaldevice controls, based on a hop count X to the donor base station, aquantity of allocated SNs not to exceed SN space/X/2. At each hop forcarried data units, a quantity of data units simultaneously transmittedover an air interface also needs to be controlled not to exceed SNspace/X/2.

Using two hops as an example, a length of a receive window of the donorbase station is 2N. It should be understood that the length of thereceive window is SN space/2, that is, the terminal device at a transmitend controls a quantity of SNs allocated to data units not to exceed2N/2=N. As shown in FIG. 13 , it can be ensured that a data unitreceived by PDCP of the donor base station at a receive end is notbeyond the receive window, thereby avoiding a packet loss phenomenongenerated on the donor base station because a data unit is beyond thereceive window.

It should be noted that in the description of the foregoing embodiment,in an uplink transmission scenario, the first device may be a terminaldevice, and the second device may be a donor base station. In a downlinktransmission scenario, the first device may be a donor base station, andthe second device may be a terminal device. This is not limited in thisapplication.

In the technical solution of this embodiment of this application, amaximum quantity of data units that a transmit end is allowed totransmit is controlled, thereby avoiding a packet loss problem generatedbecause a data unit is beyond a receive window of a receive end, andimproving accuracy of data transmission and efficiency of datatransmission.

FIG. 16 is a schematic flowchart of a data processing method 900according to an embodiment of this application. The communication method900 may be applied to a downlink transmission scenario in the scenarioshown in FIG. 2 , or certainly may be applied to another communicationscenario. This is not limited in this application. The communicationmethod 900 includes the following steps.

S910. A first device receives, by using at least one relay node, a firstdata unit transmitted by the second device, where the first data unitcarries a count value. The first device communicates with the seconddevice by using the at least one relay node. The at least one relay nodedoes not have a packet data convergence protocol PDCP entity. Forexample, a terminal device receives a first data unit transmitted by adonor base station, where the first data unit carries a count value. Asshown in FIG. 3 , each data unit has a count value and is transmittedover an air interface of a transmit end (transmitting device) inascending order of count values of data units.

It should be noted that the first device in this embodiment of thisapplication may be a terminal device. A data unit transmitted over anair interface carries a count value, and a transmit end (for example,the donor base station) still has a transmit window, that is, transmitsa data packet whose count is in a range, but a receive end (for example,the terminal device) does not have a maximum edge of a receive window.

Optionally, in an embodiment of this application, the first data unit isin a first sequence range. To be specific, the first data unit is in thetransmit window of the transmit end.

Optionally, in an embodiment of this application, the first sequencerange is used to indicate a range of count values that the second deviceis allowed to allocate or a range of count values that the second deviceis allowed to allocate when transmitting the first data unit. To bespecific, the second device needs to transmit the first data unit in arange allowed by the transmit window. The first data unit transmitted bythe second device needs to be in the range allowed by the transmitwindow during transmission.

Optionally, in an embodiment of this application, the first sequencerange is half of a sequence number space or less than half of a sequencenumber space. To be specific, a maximum quantity of data units allowedto be transmitted in the transmit window that exists at the transmit endis half of the sequence number space. The donor base station maytransmit data units in the first sequence range.

S920. The first device processes the first data unit based on the countvalue carried in the first data unit.

For example, the terminal device processes the first data unit based onthe count value of the first data unit.

Optionally, in an embodiment, if the count value of the first data unitis greater than a count value next to a count value of a last data unitcurrently already delivered, the first data unit is stored.

For example, if the count value of the last data unit already deliveredis 10, the count value next to the count value of the last data unitalready delivered is 11. If the count value of the first data unit is12, the terminal device stores the first data unit.

It should be understood that when the count value of the first data unitis greater than the count value next to the count value of the last dataunit currently already delivered, it indicates that the terminal devicehas not stored the first data unit. The terminal device first stores thefirst data unit and delivers the data units to an upper layer of a PDCPentity in order.

If the count value of the first data unit is equal to the count valuenext to the count value of the last data unit currently alreadydelivered, the first data unit is delivered to the upper layer of thepacket data convergence protocol PDCP entity.

For example, if the count value of the last data unit already deliveredis 10, the count value next to the count value of the last data unitalready delivered is 11. If the count value of the first data unit is11, the terminal device delivers the first data unit to the upper layerof the PDCP entity.

If the count value of the first data unit is less than the count valuenext to the count value of the last data unit currently alreadydelivered, the first data unit is discarded.

For example, if the count value of the last data unit already deliveredis 10, the count value next to the count value of the last data unitalready delivered is 11. If the count value of the first data unit is 9,the first data unit is discarded.

It should be understood that when the count value of the first data unitis less than the count value next to the count value of the last dataunit currently already delivered, it indicates that the terminal devicehas stored the first data unit. In this case, when receiving the dataunit again, the terminal device discards the data unit.

In an embodiment of this application, in an uplink transmissionscenario, the second device transmits the first data unit to the firstdevice by using the at least one relay node, where the first data unitcarries the count value. The first device communicates with the seconddevice by using the at least one relay node, and the at least one relaynode does not have the packet data convergence protocol PDCP entity. Thefirst data unit belongs to the first sequence range. The first sequencerange is used to indicate the range of count values that the seconddevice is allowed to allocate or the range of count values that thesecond device is allowed to allocate when transmitting the first dataunit.

Optionally, a size of the first sequence range is half of the sequencenumber space or less than half of the sequence number space.

It should be noted that in the description of the foregoing embodiment,in a downlink transmission scenario, the first device may be a terminaldevice, and the second device may be a donor base station. In an uplinktransmission scenario, the first device may be a donor base station, andthe second device may be a terminal device. This is not limited in thisapplication.

In the technical solution of this embodiment of this application, amaximum edge of a transmit window exists at a transmit end, a maximumedge of a receive window does not exist at a receive end, and a dataunit carrying a count value is transmitted, so that the data unit isprocessed, thereby avoiding a packet loss problem generated because adata unit is beyond the receive window of the receive end, and improvingaccuracy of data transmission and efficiency of data transmission.

It should be understood that sequence numbers of the foregoing processesdo not mean execution sequences in various embodiments of thisapplication. The execution sequences of the processes should bedetermined based on functions and internal logic of the processes, andshould not be construed as any limitation on the implementationprocesses of the embodiments of this application.

The data processing methods according to the embodiments of thisapplication are described in detail above. In this application, thefirst device determines the second sequence range based on the firstinformation. Specifically, the first device receives the firstinformation by using the at least one relay node, where the firstinformation is used to indicate the data unit that the second device hasreceived and/or has not received in the first data unit group, therebyimproving accuracy of data transmission and efficiency of datatransmission. It should be understood that a data processing device inthe embodiments of this application may perform each method in theforegoing embodiments of this application. To be specific, for aspecific working process of each product, refer to the correspondingprocess in the foregoing method embodiments.

The following describes embodiments of communications devices in thisapplication in detail with reference to FIG. 17 to FIG. 20 . It shouldbe understood that the description of the method embodiments correspondsto the description of the embodiments of the communications devices.Therefore, for parts that are not described in detail, refer to theforegoing method embodiments.

FIG. 17 is a schematic block diagram of a communications device 1200 fordata processing according to an embodiment of this application. In anuplink transmission scenario, the communications device 1200 maycorrespond to the first device in each method embodiment, and may haveany function of the first device in the method.

As shown in FIG. 17 , the communications device 1200 may include atransceiver module 1210 and a processing module 1220.

The transceiver module 1210 and the processing module 1220 communicatewith each other by using an internal connection path, for transfer acontrol and/or data signal. In a possible design, the transceiver module1210 and the processing module 1220 may be implemented by using chips,to implement corresponding functions of a terminal device in anembodiment of this application.

In an embodiment of this application, the communications device 1200communicates with a second device by using at least one relay node, andthe at least one relay node does not have a packet data convergenceprotocol PDCP entity. In an uplink transmission scenario, thecommunications device 1200 may be a terminal device, and the seconddevice may be a donor base station. The communications device 1200includes a transceiver module 1210 and a processing module 1220.

The transceiver module 1210 is configured to transmit a first data unitgroup, where the first data unit group is in a first sequence range.

The transceiver module 1210 is further configured to receive firstinformation by using the at least one relay node, where the firstinformation is used to indicate a data unit that the second device hasreceived and/or has not received in the first data unit group.

The processing module 1220 is configured to determine a second sequencerange based on the first information.

It should be understood that the first sequence range may be a transmitwindow of a transmit end. The terminal device may transmit a data unitin the first sequence range.

Optionally, the processing module 1220 is further configured to:

if the first information includes information about successful receptionof N consecutive data units starting from the first data unit in thefirst sequence range, obtain the second sequence range by shifting thefirst sequence range by N sequences, where N is a positive integer.

Optionally, the transceiver module 1210 is further configured to:

receive a first message transmitted by the second device and forwardedby the at least one relay node, where the first message includes thefirst information.

Optionally, the first message is a status report of a PDCP entity; orthe first message is a status report of a radio link control RLC entity.

Optionally, the first message is a periodically transmitted message.

Optionally, the transceiver module 1210 is further configured to:

transmit a query request to the second device.

Optionally, the transceiver module 1210 is further configured to:

receive a second message obtained by the at least one relay node basedon a first message transmitted by the second device, where the secondmessage includes the first information.

Optionally, the second message is determined by the at least one relaynode based on the first message and a mapping relationship betweennumbers of data units transmitted and received that is maintained by theat least one relay node.

Optionally, the second message is a status report of an RLC entity.

It should be understood that in the description of the foregoingembodiment, in an uplink transmission scenario, the first device may bea terminal device, and the second device may be a donor base station. Ina downlink transmission scenario, the first device may be a donor basestation, and the second device may be a terminal device. This is notlimited in this application.

In an embodiment of this application, the communications device 1200communicates with a second device by using at least one relay node, andthe at least one relay node does not have a packet data convergenceprotocol PDCP entity. In an uplink transmission scenario, thecommunications device 1200 may be a terminal device, and the seconddevice may be a donor base station. The communications device 1200includes a transceiver module 1210 and a processing module 1220.

The transceiver module 1210 is configured to receive a third message,where the third message includes hop count information for communicationbetween the first device and the second device.

The processing module 1220 is configured to determine a first sequencerange based on the hop count information, where the first sequence rangeis used to indicate a range of sequence numbers allocated by the firstdevice or used to indicate a maximum quantity of data units that areallowed to be transmitted.

For example, the terminal device receives a third message, where thethird message includes hop count information. If the terminal devicecommunicates with the donor base station by using one relay node, thehop count information is two hops; or if the terminal devicecommunicates with the donor base station by using two relay nodes, thehop count information is three hops.

Optionally, the first sequence range is less than or equal to a quantityof allocated sequence numbers, and the quantity of allocated sequencenumbers is a sequence number space divided by a hop count and thendivided by 2.

Optionally, the third message is a broadcast message.

Optionally, the third message is a message transmitted by usingdedicated signaling.

Optionally, the third message is transmitted by the second device.

For example, the third message is a message transmitted by the donorbase station.

Optionally, the third message is transmitted by the at least one relaynode.

It should be understood that in the description of the foregoingembodiment, in a downlink transmission scenario, the first device may bea terminal device, and the second device may be a donor base station. Inan uplink transmission scenario, the first device may be a donor basestation, and the second device may be a terminal device. This is notlimited in this application.

In an embodiment of this application, the communications device 1200communicates with a second device by using at least one relay node, andthe at least one relay node does not have a packet data convergenceprotocol PDCP entity. In an uplink transmission scenario, thecommunications device 1200 may be a terminal device, and the seconddevice may be a donor base station. The communications device 1200includes a transceiver module 1210 and a processing module 1220.

The transceiver module 1210 is configured to receive, by using the atleast one relay node, a first data unit transmitted by the seconddevice, where the first data unit carries a count value.

The processing module 1220 is configured to process the first data unitbased on the count value carried in the first data unit.

For example, the terminal device receives, by using the at least onerelay node, a first data unit transmitted by the donor base station,where the first data unit carries a count value; and

the terminal device processes the first data unit based on the countvalue carried in the first data unit.

Optionally, the processing unit 1220 is further configured to:

if the count value of the first data unit is greater than a count valuenext to a count value of a last data unit currently already delivered,store the first data unit; or

if the count value of the first data unit is equal to a count value nextto a count value of a last data unit currently already delivered,deliver the first data unit to an upper laver of a packet dataconvergence protocol PDCP entity; or

if the count value of the first data unit is less than a count valuenext to a count value of a last data unit currently already delivered,discard the first data unit.

Optionally, the processing unit 1220 is further configured to:

store the first data unit, and deliver the first data unit to the upperlayer of the PDCP entity in order based on the count value of the firstdata unit.

For example, if the count value of the last data unit already deliveredis 10, the count value next to the count value of the last data unitalready delivered is 11. If the count value of the first data unit is12, the terminal device stores the first data unit.

It should be understood that when the count value of the first data unitis greater than the count value next to the count value of the last dataunit currently already delivered, it indicates that the terminal devicehas not stored the first data unit. The terminal device first stores thefirst data unit and delivers the data units to the upper layer of thePDCP entity in order.

If the count value of the first data unit is equal to the count valuenext to the count value of the last data unit currently alreadydelivered, the first data unit is delivered to the upper layer of thepacket data convergence protocol PDCP entity.

For example, if the count value of the last data unit already deliveredis 10, the count value next to the count value of the last data unitalready delivered is 11. If the count value of the first data unit is11, the terminal device delivers the first data unit to the upper layerof the PDCP entity.

If the count value of the first data unit is less than the count valuenext to the count value of the last data unit currently alreadydelivered, the first data unit is discarded.

For example, if the count value of the last data unit already deliveredis 10, the count value next to the count value of the last data unitalready delivered is 11. If the count value of the first data unit is 9,the first data unit is discarded.

It should be understood that when the count value of the first data unitis less than the count value next to the count value of the last dataunit currently already delivered, it indicates that the terminal devicehas stored the first data unit. In this case, when receiving the dataunit again, the terminal device discards the data unit.

Optionally, the first data unit is in the first sequence range.

Optionally, the first sequence range indicates a range of count valuesthat the second device is allowed to allocate.

Optionally, the first sequence range indicates a range of count valuesthat the second device is allowed to allocate when transmitting thefirst data unit.

Optionally, a size of the first sequence range is half of a sequencenumber space or less than half of a sequence number space.

A transmission part of the second device needs to be supplemented.

It should be noted that in the description of the foregoing embodiment,in a downlink transmission scenario, the first device may be a terminaldevice, and the second device may be a donor base station. In an uplinktransmission scenario, the first device may be a donor base station, andthe second device may be a terminal device. This is not limited in thisapplication.

FIG. 18 is a schematic block diagram of a communications device 1300 fordata processing according to an embodiment of this application. Thecommunications device 1300 may correspond to the relay node in eachmethod embodiment, and may have any function of the relay node in themethod.

In an embodiment of this application, a first device communicates with asecond device by using at least one communications device 1300, and theat least one communications device 1300 does not have a packet dataconvergence protocol PDCP entity.

As shown in FIG. 13 , the communications device 1300 may include atransceiver module 1310 and a processing module 1320.

The transceiver module 1310 and the processing module 13220 communicatewith each other by using an internal connection path, for transfer acontrol and/or data signal. In a possible design, the transceiver module13210 and the processing module 1320 may be implemented by using chips,to implement corresponding functions of a terminal device in anembodiment of this application.

As shown in FIG. 18 , the communications device 1300 may include atransceiver module 1310 and a processing module 1320.

It should be noted that the communications device 1300 may be a firstrelay node directly connected to the first device, that is, an end relaynode, or may be a second relay node connected to a first relay node,that is, an intermediate relay node.

In an embodiment of this application, when the communications device1300 is the first relay node, the communications device 1300 is thefirst relay node directly connected to the first device. Thecommunications device 1300 includes a transceiver module 1310 and aprocessing module 1320.

The transceiver module 1310 is configured to receive first informationtransmitted by a previous-hop relay node of the first relay node or thesecond device, where the first information is used to indicate a dataunit that the second device has received and/or has not received in afirst data unit group, and the first data unit group is in a firstsequence range.

The processing module 1320 is configured to forward the firstinformation by the first relay node.

In an embodiment of this application, when the communications device1300 is the first relay node, the communications device 1300 is thefirst relay node directly connected to the first device. Thecommunications device 1300 includes a transceiver module 1310 and aprocessing module 1320.

The transceiver module 1310 is configured to receive first informationtransmitted by the second device, where the first information is used toindicate a data unit that the second device has received and/or has notreceived in a first data unit group, and the first data unit group is ina first sequence range.

The processing module 1320 is configured to generate second information,where the second information is determined based on a mappingrelationship between numbers of data units transmitted and received thatis maintained by the first relay node and the first information.

The transceiver module 1310 is further configured to transmit the secondinformation.

In an embodiment of this application, when the communications device1300 is the first relay node, the communications device 1300 is thefirst relay node directly connected to the first device. Thecommunications device 1300 includes a transceiver module 1310 and aprocessing module 1320.

The transceiver module 1310 is configured to receive a first data unitgroup transmitted by the first device.

The processing module 1320 is configured to add numbers to data units inthe first data unit group based on receiving order.

Optionally, numbers are added by the communications device 1300. Forexample, the communications device 1300 is the first relay node, and thefirst relay node is a relay node that directly communicates with theterminal device.

Optionally, an adaptation layer of the communications device 1300 has anordering function; and/or

the adaptation layer of the communications device 1300 has a numberingfunction.

For example, an adaptation layer of the first relay node has an orderingfunction; and/or

the adaptation layer of the first relay node has a numbering function.

Optionally, the adaptation layer is located above a radio link controlRLC entity.

Optionally, the adaptation layer is located above a media access controlMAC entity.

In an embodiment of this application, when the communications device1300 is the first relay node, the communications device 1300 is thefirst relay node directly connected to the first device. Thecommunications device 1300 includes a transceiver module 1310 and aprocessing module 1320.

The transceiver module 1310 is configured to receive a data unit havinga number and transmitted by the at least one relay node.

The processing module 1320 is configured to order the data unit based onthe number.

The transceiver module 1310 is further configured to transmit a firstdata unit group to the first device in order based on the number, wherethe first data unit group includes the ordered data unit.

Optionally, an adaptation layer has an ordering function; or

a radio link control RLC entity has an ordering function.

Optionally, the adaptation layer is located above the radio link controlRLC entity.

Optionally, the adaptation layer is located above a media access controlMAC entity.

In an embodiment of this application, when the communications device1300 is the first relay node, the communications device 1300 is thefirst relay node directly connected to the first device. Thecommunications device 1300 includes a transceiver module 1310 and aprocessing module 1320.

The processing module 1320 is configured to determine first hop countinformation, where the first relay node is a relay node that directlycommunicates with the first device.

The transceiver module 1310 is configured to transmit a third message tothe first device, where the third message includes the first hop countinformation, and the first hop count information is a quantity of the atleast one relay node or a quantity of the at least one relay node plus1.

Optionally, the transceiver module 1310 is configured to transmit thethird message to the first device by broadcast.

Optionally, the transceiver module 1310 is configured to transmit thethird message to the first device by using dedicated signaling.

Optionally, the transceiver module 1310 is configured to obtain thefirst hop count information by adding 1 to second hop count informationbroadcast by a previous-hop relay node of the first relay node.

In an embodiment of this application, when the communications device1300 is the second relay node, the communications device 1300 is thesecond relay node directly connected to the relay node. Thecommunications device 1300 includes a transceiver module 1310 and aprocessing module 1320.

The transceiver module 1310 is configured to receive a data unittransmitted by a relay node that is connected to the second relay node,where the data unit has a number.

The processing module 1320 is configured to order the data unit havingthe number.

Optionally, the number is added by the first relay node, and the firstrelay node is a relay node that directly communicates with the terminaldevice.

Optionally, an adaptation layer of the first relay node has theordering; and/or

the adaptation layer of the first relay node has a numbering function.

Optionally, an adaptation layer of the communications device 1300 has anordering function; or

a radio link control RLC entity of the communications device 1300 has anordering function.

For example, an adaptation layer of the second relay node has theordering function; or

a radio link control RLC entity of the second relay node has theordering function.

Optionally, the adaptation layer is located above the radio link controlRLC entity.

Optionally, the adaptation layer is located above a media access controlMAC entity.

In an embodiment of this application, when the communications device1300 is the second relay node, the communications device 1300 is thesecond relay node directly connected to the relay node. Thecommunications device 1300 includes a transceiver module 1310 and aprocessing module 1320.

The transceiver module 1310 is configured to receive a data unittransmitted by a relay node that is connected to the communicationsdevice 1300, where the data unit has a number.

The processing module 1320 is configured to order the data unit havingthe number.

Optionally, the number is added by an adaptation layer of the seconddevice; or

the number is added by a relay node that directly communicates with thecommunications device 1300.

Optionally, an adaptation layer of the communications device 1300 has anordering function; or

a radio link control RLC entity has an ordering function.

Optionally, the adaptation layer is located above the radio link controlRLC entity.

Optionally, the adaptation layer is located above a media access controlMAC entity.

It should be understood that in the description of the foregoingembodiment, in an uplink transmission scenario, the first device may bea terminal device, and the second device may be a donor base station. Ina downlink transmission scenario, the first device may be a donor basestation, and the second device may be a terminal device. This is notlimited in this application.

FIG. 19 is a schematic structural diagram of a communications device1400 according to an embodiment of this application. As shown in FIG. 19, the communications device 1400 includes one or more processors 1401,one or more memories 1402, and one or transceivers 1403. The processor1401 is configured to control the transceiver 1403 to transmit orreceive a signal. The memory 1402 is configured to store a computerprogram. The processor 1401 is configured to invoke and run the computerprogram in the memory 1402, so that the communications device performs acorresponding procedure and/or operation performed by the communicationsdevice in the embodiment of the transmission method in this application.

The processor 1401 may be configured to perform a correspondingoperation and/or function of the processing module 1220 in thecommunications device 1200. The transceiver 1403 may be configured toperform a corresponding operation and/or function of the transceivermodule 1210 in the communications device 1200. For brevity, details arenot described herein.

FIG. 20 is a schematic structural diagram of a communications device1500 according to an embodiment of this application. As shown in FIG. 20, the communications device 1500 includes one or more processors 1501,one or more memories 1502, and one or transceivers 1503. The processor1501 is configured to control the transceiver 1503 to transmit orreceive a signal. The memory 1502 is configured to store a computerprogram. The processor 1501 is configured to invoke and run the computerprogram in the memory 1502, so that the communications device performs acorresponding procedure and/or operation performed by the communicationsdevice in the embodiment of the transmission method in this application.

The processor 1501 may be configured to perform a correspondingoperation and/or function of the processing module 1320 in thecommunications device 1300. The transceiver 1503 may be configured toperform a corresponding operation and/or function of the transceivermodule 1310 in the communications device 1300. For brevity, details arenot described herein.

An embodiment of this application further provides a system-on-chip,applied to a communications device. The system-on-chip includes at leastone processor, at least one memory, and an interface circuit. Theinterface circuit is responsible for information exchange between thesystem-on-chip and the outside. The at least one memory, the interfacecircuit, and the at least one processor are interconnected by cables.The at least one memory stores an instruction, and the at least oneprocessor executes the instruction to perform an operation performed bythe communications device in the method in each of the foregoingaspects.

An embodiment of this application further provides a communicationssystem, including a communications device and/or a network device, wherethe communications device is the communications device in each of theforegoing aspects.

An embodiment of this application further provides a computer programproduct, applied to a communications device, where the computer programproduct includes a series of instructions, and when the instruction isrun, an operation performed by the communications device in the methodin each of the foregoing aspects is performed.

Terminologies such as “component”, “module”, and “system” used in thisapplication are used to indicate computer-related entities, hardware,firmware, combinations of hardware and software, software, or softwarebeing executed. For example, a component may be, but is not limited to,a process that runs on a processor, a processor, an object, anexecutable file, an execution thread, a program, and/or a computer. Asshown in figures, both a computing device and an application that runson the computing device may be components. One or more components mayreside within a process and/or an execution thread, and a component maybe located on one computer and/or distributed between two or morecomputers. In addition, these components may be executed from variouscomputer-readable media that store various data structures. Thecomponents may perform communication by using a local and/or remoteprocess based on a signal having one or more data packets (for example,data from two components interacting with another component in a localsystem, a distributed system, and/or a network, such as the internetinteracting with other systems by using signals).

It should be understood that the manners, cases, and types in theembodiments of this application, and division of the embodiments aremerely for ease of description, and should not constitute a particularlimitation. Each manner, type, and case, and features of the embodimentsmay be combined when there is no contradiction.

It should also be understood that in each embodiment of thisapplication, terms such as “first”, “second”, and “third” are merelyintended to specify different objects, and do not indicate otherlimitations on the specified objects.

In addition, the terms “system” and “network” may be usedinterchangeably in this specification. The term “and/or” in thisspecification describes only an association relationship for describingassociated objects and represents that three relationships may exist.For example, A and/or B may represent the following three cases. Only Aexists, both A and B exist, and only B exists. In addition, thecharacter “/” in this specification usually indicates an “or”relationship between the associated objects.

It should be understood that in the embodiments of this application, “Bcorresponding to A” indicates that B is associated with A, and B may bedetermined according to A. However, it should further be understood thatdetermining B according to A does not mean that B is determinedaccording to A only, but B may be alternatively determined according toA and/or other information.

All or some of the foregoing embodiments may be implemented throughsoftware, hardware, firmware, or any combination thereof. When softwareis used to implement the embodiments, the embodiments may be implementedcompletely or partially in a form of a computer program product. Thecomputer program product includes one or more computer instructions.When the computer program instructions are loaded and executed on acomputer, the procedures or functions according to the embodiments ofthe present invention are completely or partially generated. Thecomputer may be a general-purpose computer, a dedicated computer, acomputer network, or other programmable apparatuses. The computerinstructions may be stored in a computer-readable storage medium or maybe transmitted from a computer-readable storage medium to anothercomputer-readable storage medium. For example, the computer instructionsmay be transmitted from a website, computer, server, or data center toanother website, computer, server, or data center in a wired (forexample, a coaxial cable, an optical fiber, or a digital subscriber line(digital subscriber line, DSL)) or wireless (for example, infrared,radio, or microwave) manner. The computer-readable storage medium may beany usable medium accessible by a computer, or a data storage device,such as a server or a data center, integrating one or more usable media.The usable medium may be a magnetic medium (for example, a floppy disk,a hard disk, or a magnetic tape), an optical medium (for example, adigital video disc (digital video disc, DVD)), a semiconductor medium(for example, a solid-state drive (solid state disk, SSD)), or the like.

A person of ordinary skill in the art may be aware that, in combinationwith the examples described in the embodiments disclosed in thisspecification, units and algorithm steps may be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraint conditions ofthe technical solution. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of this application.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, refer to acorresponding process in the foregoing method embodiments, and detailsare not described herein again.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, division into the units ismerely logical function division. There may be another division mannerin actual implementation. For example, a plurality of units orcomponents may be combined or integrated into another system, or somefeatures may be ignored or not performed. In addition, the displayed ordiscussed mutual couplings or direct couplings or communicationconnections may be implemented by using some interfaces. The indirectcouplings or communication connections between the apparatuses or unitsmay be implemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected based on actualrequirements to achieve the objectives of the solutions of theembodiments.

In addition, function units in the embodiments of this application maybe integrated into one processing unit, or each of the units may existalone physically, or two or more units may be integrated into one unit.

When the functions are implemented in a form of a software function unitand sold or used as an independent product, the functions may be storedin a computer-readable storage medium. Based on such an understanding,the technical solutions of this application essentially, or the partcontributing to the prior art, or some of the technical solutions may beimplemented in a form of a software product. The computer softwareproduct is stored in a storage medium, and includes several instructionsfor instructing a computer device (which may be a personal computer, aserver, or a network device) to perform all or some of the steps of themethods described in the embodiments of this application. The foregoingstorage medium includes: any medium that can store program code, such asa USB flash drive, a removable hard disk, a read-only memory (read-onlymemory, ROM), a random access memory (random access memory, RAM), amagnetic disk, or an optical disc.

The foregoing descriptions are merely specific implementations of thisapplication, but are not intended to limit the protection scope of thisapplication. Any variation or replacement readily figured out by aperson skilled in the art within the technical scope disclosed in thisapplication shall fall within the protection scope of this application.Therefore, the protection scope of this application shall be subject tothe protection scope of the claims.

What is claimed is:
 1. A method implemented by a second relay node,wherein the second relay node does not comprise a Packet DataConvergence Protocol (PDCP) entity, and wherein the method comprises:receiving a plurality of data units from a first relay node coupled tothe second relay node, wherein each data unit of the plurality of dataunits comprises a sequence number; and performing numbering of theplurality of data units based on an order of receiving the plurality ofdata units from the first relay node; and transmitting the plurality ofdata units to a second device based on the numbering of the plurality ofdata units, wherein the second device determines which data units arewithin a transmit window based on the numbering and then reorders theplurality of data units based on the sequence number of each data unit.2. The method of claim 1, further comprising adding the sequence numberto each data unit of the plurality of data units by the first relaynode, wherein the first relay node directly communicates with a firstdevice.
 3. The method of claim 2, wherein an adaptation layer of thefirst relay node comprises a numbering function, or wherein a Radio LinkControl (RLC) entity of the first relay node comprises a second orderingfunction.
 4. The method of claim 3, wherein the adaptation layer islocated above the RLC entity.
 5. The method of claim 3, wherein theadaptation layer is located above a media access control (MAC) entity.6. The method of claim 1, wherein the second device is configured to:perform ordering of the plurality of data units based on the numberingof the plurality of data units; deliver the ordered plurality of dataunits to a PDCP layer of the second device; and perform, by the PDCPlayer, further ordering of the plurality of data units based on thesequence number of each data unit of the plurality of data units.
 7. Themethod of claim 1, wherein performing numbering of the plurality of dataunits comprises uniquely numbering each data unit of the plurality ofdata units.
 8. A method implemented by a second device, comprising:receiving a plurality of data units from a second relay node, whereinthe second relay node transmits the plurality of data units based on anumbering of the plurality of data units; performing ordering of theplurality of data units based on the numbering; delivering the orderedplurality of data units to a Packet Data Convergence Protocol (PDCP)layer of the second device; and performing, by the PDCP layer, furtherordering of the plurality of data units based on a sequence number ofeach data unit of the plurality of data units.
 9. The method of claim 8,wherein the second relay node does not comprise a PDCP entity, whereinthe second relay node receives the plurality of data units from a firstrelay node coupled to the second relay node, and wherein the secondrelay node performs the numbering of the plurality of data units basedon a received order of the plurality of data units at the second relaynode.
 10. The method of claim 9, wherein the sequence number of eachdata unit is added by the first relay node.
 11. The method of claim 10,wherein an adaptation layer of the first relay node comprises anumbering function, or wherein a Radio Link Control (RLC) entity of thefirst relay node comprises a second ordering function.
 12. The method ofclaim 9, wherein the sequence number of each data unit is added by afirst device transmitting the plurality of data units to the first relaynode.
 13. The method of claim 12, wherein the numbering of the pluralityof data units is added by the first relay node.
 14. The method of claim8, wherein a Radio Link Control (RLC) entity of the second relay nodecomprises an ordering function.
 15. A second device comprising: a memoryconfigured to store instructions; and a processor coupled to the memory,wherein the instructions cause the processor to be configured to:receive a plurality of data units from a second relay node, wherein thesecond relay node transmits the plurality of data units based on anumbering of the plurality of data units; perform ordering of theplurality of data units based on the numbering; deliver the orderedplurality of data units to a Packet Data Convergence Protocol (PDCP)layer of the second device; and perform, by the PDCP layer, furtherordering of the plurality of data units based on a sequence number ofeach data unit of the plurality of data units.
 16. The second device ofclaim 15, wherein the second relay node does not comprise a PDCP entity,wherein the second relay node receives the plurality of data units froma first relay node coupled to the second relay node, and wherein thesecond relay node performs the numbering of the plurality of data unitsbased on a received order of the plurality of data units at the secondrelay node.
 17. The second device of claim 16, wherein the sequencenumber of each data unit is added by the first relay node.
 18. Thesecond device of claim 17, wherein an adaptation layer of the firstrelay node comprises a numbering function, or wherein a Radio LinkControl (RLC) entity of the first relay node comprises a second orderingfunction.
 19. The second device of claim 16, wherein the sequence numberof each data unit is added by a first device transmitting the pluralityof data units to the first relay node.
 20. The second device of claim19, wherein the numbering of the plurality of data units is added by thefirst relay node.